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Contents

Python

Python

Python is a programming language that lets you work more quickly and integrate your systems more effectively.

Links:

Python3

Install from SlackBuild

   1 cd /tmp
   2 wget http://slackbuilds.org/slackbuilds/13.1/development/python3.tar.gz
   3 tar xvzf python3.tar.gz
   4 cd python3
   5 wget http://python.org/ftp/python/3.1.3/Python-3.1.3.tar.bz2
   6 ./python3.SlackBuild
   7 installpkg /tmp/python3-3.1.1-i486-1_SBo.tgz

UTF-8

At the start of source code files:

   1 # -*- coding: utf-8 -*-
   2 print u"Olá mundo" # hello world in portuguese

Letter á is encoded as hexadecimal 0xC3A1 in UTF-8 and as 0x00E1 in UTF-16. http://www.fileformat.info/info/unicode/char/e1/index.htm

Letter ú is encoded as hexadecimal 0xC3BA in UTF-8, as 0x00FA in UTF-16 and as 0xFA in latin-1/ISO8859-1/CP-1252.

   1 #utf-8 data
   2 utf81 ='\xc3\xba' 
   3 # convert from utf-8 to unicode
   4 unic = utf81.decode('utf-8') 
   5 
   6 for c in unic:
   7     print '%04X'%(ord(c))
   8 # convert from unicode to latin1/ISO8859-1 CP-1252
   9 lat1=unic.encode('latin1') 
  10 for c in lat1:
  11     print '%02X'%(ord(c))

Utf-8 and Unicode

   1 utf81='\xe1\xb7\x97' #utf-8 data
   2 
   3 unic = utf81.decode('utf-8') #converts from utf-8 to unicode (utf-16)
   4 for c in unic:
   5     print '%04X'%(ord(c))
   6 type(unic) # unicode, 2 bytes per char
   7 type(utf81) # str, 1 bytes per char

   1 # python3 example
   2 a=u'cão' # string in utf-8
   3 x=bytes(a,'utf-8') # convert string in utf-8 to bytes representation
   4 print(dir(a))
   5 print(dir(x))
   6 print(type(a))
   7 print(type(x))
   8 b = x.decode() # convert bytes again to an utf-8 string
   9 print(dir(b))
  10 print(type(b))

Time and date

   1 import time
   2 # get seconds since epoch until now in UTC to a string year-month-dayThour:minute:second
   3 strutc = time.strftime('%Y-%m-%dT%H:%M:%S', time.gmtime() ) 
   4 # get seconds since epoch until now  in localtime to a string  year-month-dayThour:minute:second
   5 strlocal = time.strftime('%Y-%m-%dT%H:%M:%S', time.localtime() ) 
   6 # number seconds since epoch
   7 nrSeconds = time.mktime(time.gmtime())
   8 nrSeconds = time.time() #usually is UTC on all OS
   9 # from timestamp to string date
  10 import datetime
  11 print(datetime.datetime.fromtimestamp(1284101485).strftime('%Y-%m-%d %H:%M:%S'))
  12 #
  13 def toUTCDateStr(timestamp):
  14     return datetime.datetime.utcfromtimestamp( timestamp ).strftime('%Y-%m-%d %H:%M:%S ')
  15 # timedelta
  16 import datetime
  17 x=datetime.datetime.fromtimestamp(1284101485)
  18 nowx=datetime.datetime.now()                    
  19 ts=(nowx-x).total_seconds()
  20 print int(ts)
  21 ### add , subtract days
  22 import datetime
  23 x = datetime.datetime(2014,1,2)
  24 print x
  25 y = x - datetime.timedelta(days=1)
  26 print y
  27 z = y - datetime.timedelta(days=1)
  28 print z
  29 
  30 ### convert string with date to time tuple
  31 import time
  32 timeTuple = time.strptime('2014-01-01 10:11:12','%Y-%m-%d %H:%M:%S')
  33 nrSecondsSince1970=time.mktime(timeTuple)
  34 ### get seconds since epoch
  35 start = int(datetime.datetime(2014,3,9,0,0,0,0).strftime("%s"))*1000
  36 end = int(datetime.datetime(2014,3,14,23,59,59,999).strftime("%s"))*1000
  37 
  38 ### string from utc current date
  39 currutc=datetime.datetime.utcnow().strftime("%Y-%m-%d %H:%M:%S")
  40 
  41 import time
  42 help(time.strptime)
  43 tt=time.strptime('Sat Aug 14 20:28:54 UTC 2021','%a %b %d %H:%M:%S %Z %Y')
  44 nrSecondsSince1970=time.mktime(tt)
  45 
  46 # email date format
  47 >>> time.strftime('%a, %d %b %Y %H:%M:%S %z (%Z)', time.gmtime() )
  48 'Sun, 27 Feb 2022 14:17:14 +0000 (GMT)'

Write and reading data for a plist file

A plist file stores data in XML format.

   1 import plistlib
   2 value = [{'key1':123,'key2':'asdf'},{'keyx1':'testing','keyz1':'yup'}]
   3 # save value in plist file
   4 plistlib.writePlist(value,'/tmp/plist1.plist')
   5 o=plistlib.readPlist('/tmp/plist1.plist')
   6 print o

Content of the file /tmp/plist1.plist

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
   3 <plist version="1.0">
   4 <array>
   5         <dict>
   6                 <key>key1</key>
   7                 <integer>123</integer>
   8                 <key>key2</key>
   9                 <string>asdf</string>
  10         </dict>
  11         <dict>
  12                 <key>keyx1</key>
  13                 <string>testing</string>
  14                 <key>keyz1</key>
  15                 <string>yup</string>
  16         </dict>
  17 </array>
  18 </plist>

Threading

   1 #!/usr/bin/python
   2 # timestable.py
   3 # calculates the times table in concurrency
   4 import threading
   5 import time
   6 
   7 class TimesTable (threading.Thread):
   8     def __init__(self, timesTable):
   9         threading.Thread.__init__(self) #required
  10         self.timeTable = timesTable
  11         self.count = 1
  12     def run(self):
  13         loop=True
  14         while loop:
  15             time.sleep(1) #sleep for 1 second
  16             result=self.timeTable * self.count
  17             print "%d*%d=%d"%(self.timeTable,self.count,result)
  18             if self.count<10:
  19                 self.count = self.count+1
  20             else:
  21                 self.count=1
  22 
  23 # create threads
  24 timesTable2 = TimesTable(2)
  25 timesTable5 = TimesTable(7)
  26 
  27 # start the threads
  28 timesTable2.start()
  29 timesTable5.start()

unit tests (pyunit)

   1 #filename: unitTest.py
   2 #Run tests: python unitTest.py
   3 #Should fail on testAdd2
   4 import unittest
   5 
   6 class SimpleTestCase(unittest.TestCase):
   7     def setUp(self):
   8         self.res=4
   9 
  10     def tearDown(self):
  11         self.res=0
  12 
  13     def testAdd1(self):
  14         res=2+2
  15         self.assertEqual(self.res,res,'')       
  16 
  17     def testAdd2(self):
  18         res=2+3
  19         self.assertEqual(self.res,res,'')       
  20 
  21     def testAdd3(self):
  22         res=2+3
  23         self.assertNotEqual(self.res,res,'')       
  24 
  25 if __name__ == '__main__':
  26     unittest.main()

unit tests coverage (pyunit)

http://coverage.readthedocs.io/en/latest/cmd.html

   1 pip install coverage
   2 pip install --user --upgrade coverage

tests.py

   1 import unittest
   2 from impl import add 
   3 from impl import sub
   4 
   5 class TestCase(unittest.TestCase):
   6     def test_add(self):
   7         self.assertEqual(5,add(2,3))
   8 #    def test_sub(self):
   9 #        self.assertEqual(1,add(3,2))
  10 if __name__ == '__main__':
  11     unittest.main()

impl.py

   1 def add(arg1,arg2):
   2     return arg1+arg2
   3 
   4 def sub(arg1,arg2):
   5     return arg-+arg2

Steps:

coverage erase
coverage run tests.py
coverage report -m impl.py
coverage html impl.py #in htmlcov folder

unit tests - mock

   1 from unittest.mock import MagicMock
   2 
   3 class X(object):
   4     def getX(self):
   5         return 111
   6 
   7 if __name__=='__main__':
   8     x = X()
   9     print(x.getX())
  10     x.getX = MagicMock(return_value=999)
  11     print( x.getX() )

cython

https://cython.org/

Cython is an optimising static compiler for both the Python programming language and the extended Cython programming language (based on Pyrex).

Installation:

   1 su
   2 cd /tmp
   3 wget http://cython.org/release/Cython-0.19.1.tar.gz
   4 tar xvzf Cython-0.19.1.tar.gz 
   5 cd Cython-0.19.1
   6 python setup.py build
   7 python setup.py install

pymssql

Requires cython. Installation:

   1 su
   2 cd /tmp
   3 wget [[http://pymssql.googlecode.com/files/pymssql-2.0.0b1-dev-20111019.tar.gz]]
   4 tar xvvzf pymssql-2.0.0b1-dev-20111019.tar.gz
   5 cd pymssql-2.0.0b1-dev-20111019
   6 python setup.py build
   7 python setup.py install
   8 python
   9 import pymssql

pywhois

Python module for retrieving WHOIS information of domains http://code.google.com/p/pywhois/.

Fetch code with mercurial:

   1 cd /tmp
   2 hg clone https://code.google.com/p/pywhois/
   3 cd pywhois
   4 python setup.py build
   5 python setup.py install

Syntax highlighting on Vim for wsgi

Edit ~./.vimrc:

   1 syntax on
   2 filetype on
   3 au BufNewFile,BufRead *.wsgi set filetype=python

Get file modification time

   1 import os
   2 nrSeconds=os.path.getmtime('/folder/file') # unix epoch, nr secs since 1970-01-01 00:00:00

Kill process with PID

   1 import os
   2 import signal
   3 os.kill(pid,signal.SIGTERM)

Log message to /var/log/messages or /var/log/syslog

   1 import syslog
   2 syslog.syslog(syslog.LOG_INFO,'message to syslog')

   1 import syslog
   2 
   3 syslog.syslog(syslog.LOG_DEBUG,'DEBUG')
   4 syslog.syslog(syslog.LOG_INFO,'INFO')
   5 syslog.syslog(syslog.LOG_WARNING,'WARNING')
   6 syslog.syslog(syslog.LOG_ERR,'ERR')
   7 syslog.syslog(syslog.LOG_CRIT,'CRIT')

OS	File	Logged levels
Slack64 14	/var/log/messages	INFO
Slack64 14	/var/log/syslog	WARNING ERR CRIT
CentOS 6.4	/var/log/messages	INFO WARNING ERR CRIT
Ubuntu 12.04 Precise	/var/log/syslog	DEBUG INFO WARNING ERR CRIT
Debian 7.0 Wheezy	/var/log/syslog	DEBUG INFO WARNING ERR CRIT

Simple process monitor

   1 # example service, dummyService.py
   2 import time
   3 while True:
   4     try:
   5         f=open('filex.log','wb')
   6         f.write('%f'%(time.time()))
   7         f.close() 
   8         time.sleep(5)
   9     except KeyboardInterrupt:
  10         quit()

   1 #service monitor.py
   2 # * * * * * /usr/bin/python /home/vitor/svc/monitor.py
   3 import os
   4 import syslog
   5 import subprocess
   6 
   7 if __name__=="__main__":
   8     files = os.listdir('/proc')
   9     script="dummyService.py"
  10     prefix="dummyService:"
  11 
  12     svcRunning=False
  13 
  14     for file in files:
  15 
  16         if file.isdigit():
  17             cmdline = open('/proc/%s/cmdline'%(file),'r').read()
  18             proc = "%s %s "%(file,cmdline)
  19 
  20             if script  in proc :
  21                 svcRunning=True
  22 
  23     if svcRunning==False:
  24         syslog.syslog(syslog.LOG_INFO,'%s process created '%(prefix) )
  25         # run exec process on python Popen
  26         subprocess.Popen(['/usr/bin/python','dummyService.py'],cwd='/home/userx/svc')

Read URL content

   1 import urllib2
   2 r=urllib2.urlopen('http://www.sapo.pt')
   3 resp=r.read()
   4 print resp

Windows service

Install http://sourceforge.net/projects/pywin32/files/pywin32/Build%20218/pywin32-218.win32-py2.5.exe/download for Python 2.5 for Windows.

Adapted from http://ryrobes.com/python/running-python-scripts-as-a-windows-service/

   1 # C:\cmt\test>python testWinSvc.py install
   2 # C:\cmt\test>python testWinSvc.py start
   3 # C:\cmt\test>python testWinSvc.py stop
   4 # C:\cmt\test>python testWinSvc.py remove
   5 # C:\cmt\test>service.msc
   6 import win32service
   7 import win32serviceutil
   8 import win32api
   9 import win32con
  10 import win32event
  11 import win32evtlogutil
  12 import os, sys, string, time
  13 
  14 class aservice(win32serviceutil.ServiceFramework):
  15    _svc_name_ = "MyServiceShortName"
  16    _svc_display_name_ = "My Service Long Fancy Name!"
  17    _svc_description_ = "THis is what my crazy little service does - aka a DESCRIPTION! WHoa!"
  18          
  19    def __init__(self, args):
  20            win32serviceutil.ServiceFramework.__init__(self, args)
  21            self.hWaitStop = win32event.CreateEvent(None, 0, 0, None)           
  22 
  23    def SvcStop(self):
  24            self.ReportServiceStatus(win32service.SERVICE_STOP_PENDING)
  25            win32event.SetEvent(self.hWaitStop)                    
  26          
  27    def SvcDoRun(self):
  28       import servicemanager      
  29       servicemanager.LogMsg(servicemanager.EVENTLOG_INFORMATION_TYPE,servicemanager.PYS_SERVICE_STARTED,(self._svc_name_, ''))       
  30       self.timeout = 1000     #1 second
  31       # This is how long the service will wait to run / refresh itself (see script below)
  32 
  33       while 1:
  34          # Wait for service stop signal, if I timeout, loop again
  35          rc = win32event.WaitForSingleObject(self.hWaitStop, self.timeout)
  36          # Check to see if self.hWaitStop happened
  37          if rc == win32event.WAIT_OBJECT_0:
  38             # Stop signal encountered
  39             servicemanager.LogInfoMsg("SomeShortNameVersion - STOPPED!")  #For Event Log
  40             break
  41          else:
  42                  try:
  43                      handle = open('c:/windows/temp/outx1.txt', "a")
  44                      handle.write('%s \n' % ('tst svc'))
  45                      handle.close()
  46                  except:
  47                      pass
  48 
  49 
  50 
  51 def ctrlHandler(ctrlType):
  52    return True
  53                   
  54 if __name__ == '__main__':   
  55    win32api.SetConsoleCtrlHandler(ctrlHandler, True)   
  56    win32serviceutil.HandleCommandLine(aservice)

Logging

   1 import logging 
   2 logging.basicConfig(level=logging.DEBUG,
   3                     format='%(asctime)s %(name)-12s %(levelname)-8s %(message)s',
   4                     datefmt='%m-%d %H:%M',
   5                     filename='/tmp/app.log',
   6                     filemode='w')
   7 logging.info('Jackdaws love my big sphinx of quartz.')
   8 logging.info('Jackdaws love my big sphinx of quartz.')
   9 logging.info('Jackdaws love my big sphinx of quartz33.')
  10 quit()
  11 # cat /tmp/app.log

Adapted from http://docs.python.org/2/howto/logging-cookbook.html#logging-to-multiple-destinations

   1 import logging
   2 
   3 logging.basicConfig(level=logging.DEBUG, \
   4     format='%(asctime)s %(name)-12s %(levelname)-8s %(message)s', \
   5     datefmt='%Y-%m-%d %H:%M:%S %z', \
   6     filename='/tmp/myapp.log', \
   7     filemode='a')
   8 #log to console
   9 console = logging.StreamHandler()
  10 console.setLevel(logging.INFO)
  11 formatter = logging.Formatter('%(name)-12s: %(levelname)-8s %(message)s')
  12 console.setFormatter(formatter)
  13 logging.getLogger('').addHandler(console)
  14 logging.info('Jackdaws love my big sphinx of quartz.') # using default logger '' 
  15 #other loggers
  16 logger1 = logging.getLogger('myapp.area1')
  17 logger2 = logging.getLogger(__name__)
  18 logger1.debug('Quick zephyrs blow, vexing daft Jim.')
  19 logger1.info('How quickly daft jumping zebras vex.')
  20 logger2.warning('Jail zesty vixen who grabbed pay from quack.')
  21 logger2.error('The five boxing wizards jump quickly.')

Copied from http://docs.python.org/2/howto/logging-cookbook.html#configuration-server-example Logging configurable on runtime, receiving new parameters by socket

Server:

   1 import logging
   2 import logging.config
   3 import time
   4 import os
   5 
   6 # read initial config file
   7 logging.config.fileConfig('logging.conf')
   8 
   9 # create and start listener on port 9999
  10 t = logging.config.listen(9999)
  11 t.start()
  12 
  13 logger = logging.getLogger('simpleExample')
  14 
  15 try:
  16     # loop through logging calls to see the difference
  17     # new configurations make, until Ctrl+C is pressed
  18     while True:
  19         logger.debug('debug message')
  20         logger.info('info message')
  21         logger.warn('warn message')
  22         logger.error('error message')
  23         logger.critical('critical message')
  24         time.sleep(5)
  25 except KeyboardInterrupt:
  26     # cleanup
  27     logging.config.stopListening()
  28     t.join()

Client:

   1 #!/usr/bin/env python
   2 import socket, sys, struct
   3 
   4 with open(sys.argv[1], 'rb') as f:
   5     data_to_send = f.read()
   6 
   7 HOST = 'localhost'
   8 PORT = 9999
   9 s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
  10 print('connecting...')
  11 s.connect((HOST, PORT))
  12 print('sending config...')
  13 s.send(struct.pack('>L', len(data_to_send)))
  14 s.send(data_to_send)
  15 s.close()
  16 print('complete')

Logging with date rotation and email

   1 import logging
   2 from logging.handlers import TimedRotatingFileHandler
   3 from logging.handlers import SMTPHandler
   4 
   5 class Logger(object):
   6     def __init__(self):
   7         loggerName='appx'
   8         logFormatter = logging.Formatter('[%(asctime)s %(name)-12s %(levelname)-8s] %(message)s',datefmt='%Y-%m-%d %H:%M:%S %z')
   9         
  10         rotatingLogHandler = TimedRotatingFileHandler('%s.log'%(loggerName),when='midnight',utc=True)
  11         rotatingLogHandler.setFormatter(logFormatter)
  12         rotatingLogHandler.setLevel(logging.DEBUG)
  13 
  14         smtpLogHandler = SMTPHandler(mailhost='hostx.com', fromaddr='mail@hostx.com', toaddrs='dest@hostx.com', subject=loggerName, \
  15             credentials=('accountx','12345678'), secure=None)
  16         smtpLogHandler.setFormatter(logFormatter)
  17         smtpLogHandler.setLevel(logging.WARNING)
  18                         
  19         self.logger = logging.getLogger(loggerName)
  20         self.logger.addHandler(rotatingLogHandler)
  21         self.logger.addHandler(smtpLogHandler)
  22         self.logger.setLevel(logging.DEBUG)
  23         
  24     def debug(self,m):
  25         self.logger.debug(m)
  26 
  27     def info(self,m):
  28         self.logger.info(m)
  29 
  30     def warning(self,m):
  31         self.logger.warning(m)
  32         
  33     def error(self,m):
  34         self.logger.error(m)
  35         
  36     def critical(self,m):
  37         self.logger.critical(m)

pytz - World Timezone Definitions for Python

   1 import pytz
   2 import datetime
   3 
   4 #fmt = '%Y-%m-%d %H:%M:%S %Z%z'
   5 london=pytz.timezone('Europe/London')
   6 lisbon=pytz.timezone('Europe/Lisbon')
   7 paris  =pytz.timezone('Europe/Paris')
   8 utc = pytz.timezone('UTC')
   9 berlin = pytz.timezone('Europe/Berlin')
  10 
  11 print
  12 dtx = datetime.datetime(2002, 12, 27, 12, 0, 0,tzinfo=utc ) 
  13 print 
  14 print 'UTC    ' , dtx
  15 print 'London ',dtx.astimezone(london)
  16 print 'Lisbon ',dtx.astimezone(lisbon)
  17 print 'Paris  ',dtx.astimezone(paris)
  18 print 'Berlin ',dtx.astimezone(berlin)
  19 
  20 
  21 print
  22 dty = datetime.datetime(2002, 8, 27, 13, 0, 0,tzinfo=utc ) 
  23 print 'UTC    ',dty
  24 print 'London ',dty.astimezone(london)
  25 print 'Lisbon ',dty.astimezone(lisbon)
  26 print 'Paris  ',dty.astimezone(paris)
  27 print 'Berlin ',dty.astimezone(berlin)

Sort example

   1 class Acme(object):
   2     def __init__(self,valuex):
   3         self.valuex=valuex
   4 
   5     def __cmp__(self, other):
   6         if self.valuex==other.valuex:
   7             return 0
   8         if self.valuex>other.valuex:
   9             return 1
  10         if self.valuex<other.valuex:
  11             return -1
  12 
  13     def __repr__(self):
  14         return self.valuex
  15 
  16 if __name__=='__main__':
  17     listx=[]
  18     listx.append( Acme('C') )
  19     listx.append( Acme('A') )
  20     listx.append( Acme('Z') )
  21     print 'original:',listx
  22     print 'sorted asc:',sorted(listx,reverse=False)
  23     print 'sorted desc:',sorted(listx,reverse=True)
  24     listx.sort()
  25     print 'sort:',listx
  26     listx.reverse()
  27     print 'reverse:',listx

sys.path

With sys.path we are able to add new folders which serve as base path to modules. The idea is similar to classpath in Java.

Create file /tmp/testex.py

   1 def test1()
   2     print("Alright !!!!")

Run python interactively:

   1 vitor@darkstar[~]$python
   2 Python 2.7.3 (default, Jul  3 2012, 21:16:07) 
   3 [GCC 4.7.1] on linux2
   4 Type "help", "copyright", "credits" or "license" for more information.
   5 >>> import testex
   6 Traceback (most recent call last):
   7   File "<stdin>", line 1, in <module>
   8 ImportError: No module named testex
   9 >>> import sys
  10 >>> sys.path.append('/tmp') # add /tmp to modules paths
  11 >>> testex.test1()
  12 Allright !!!!

By default on Linux systems, modules are also searched in ~/.local/pythonXX.YY/site-packages. If the file testex.py would exist, it would also be used without being necessary to add the folder /tmp to the sys.path . For the user vitor and python 2.7 the path would be /home/vitor/.local/lib/python2.7/site-packages .

Math

   1 # round float to 6 decimal places
   2 nr=1.23456789
   3 print round(nr,6)
   4 # round float to 4 decimal places
   5 nr=1.23456789
   6 print round(nr,4)

SMTP

   1 import smtplib
   2 
   3 class Smtp(object):
   4     def __init__(self,server,port,user,passx,appName):
   5         self.server=server
   6         self.port=port
   7         self.user=user
   8         self.passx=passx
   9         self.appName=appName
  10 
  11     def send(self,fromx,tox,subjectx,contentType,body):
  12         s=smtplib.SMTP()
  13         s.connect(self.server,self.port)
  14         s.ehlo(self.appName)
  15         s.login(self.user,self.passx)         
  16         msg='From: %s\r\nTo: %s\r\nSubject: %s\r\nContent-Type: %s\r\n\r\n%s'%(fromx,tox,subjectx,contentType,body)
  17         s.sendmail(fromx,tox,msg)
  18         s.quit()
  19 
  20 s=Smtp('mail.example.org',25,'norep@example.org','12345678','TestApp')
  21 # content types: text/plain text/html
  22 s.send('norep@example.org',['user1@example.org','user2@example.org'],'Subject','text/plain','Body mail')

JSON serializable

   1 from json import JSONEncoder
   2 import json
   3 
   4 class EncoderJSON(JSONEncoder):
   5     def default(self, o):
   6         return o.getJSONDict()    
   7     
   8 class Acme(object):
   9     def __init__(self,paramx,valuex):
  10         self.paramx=paramx
  11         self.valuex=valuex
  12         
  13     def getJSONDict(self):
  14         return {'paramx':self.paramx ,'valuex':self.valuex}
  15                 
  16     def __repr__(self):
  17         return '%s %s %s'%(self.paramx ,self.valuex)
  18 
  19 if __name__=='__main__':
  20     listx=[]
  21     listx.append(Acme('p1','v1'))
  22     listx.append(Acme('p2','v2'))
  23     # json.dumps likes lists and dictionaries
  24     print( json.dumps(listx,cls=EncoderJSON) ) 
  25     # output [{"valuex": "v1", "paramx": "p1"}, {"valuex": "v2", "paramx": "p2"}]

Decorators

http://simeonfranklin.com/blog/2012/jul/1/python-decorators-in-12-steps/

Wraps functions with functionality, before, after , changes parameters of the decorated function.

   1 #decorator logger
   2 def logger(func):
   3         def inner(*args, **kwargs): # step 1
   4             print "Arguments were: %s, %s" % (args, kwargs)
   5             return func(*args, **kwargs) # step 2
   6         return inner
   7 
   8 @logger
   9 def foo1(x, y=1):
  10     return x * y
  11 if __name__=='__main__':
  12     foo1(2,2)

   1 import sys
   2 from os import path 
   3 #decorator adder
   4 def add_one_args(decoratedFunction):
   5     def interceptor(*args, **kwargs): # step 1
   6         print "Arguments were: args %s, kwargs %s" % (args, kwargs)
   7         index=0
   8         new_args=[]
   9         # change input 
  10         isnotint=False
  11         for arg in args:
  12             if isinstance(arg,int):                    
  13                 new_args.append(arg+1)
  14             else:
  15                 isnotint=True
  16             index=index+1
  17                 
  18         if isnotint==False: 
  19             args=tuple(new_args)
  20 
  21         new_kwargs={}
  22         for kwarg in kwargs:
  23             new_kwargs[kwarg] = kwargs[kwarg]+1
  24 
  25         decoratedFuncReturn =  decoratedFunction(*args, **new_kwargs) # step 2
  26         # change output
  27         decoratedFuncReturn = decoratedFuncReturn * 2
  28         return decoratedFuncReturn
  29     return interceptor
  30 
  31 @add_one_args
  32 def foo1(x, y=1):
  33     print('Got arguments in foo1 %d %d'%(x,y))
  34     mul = x * y
  35     print('Multiplication result inside function %d'%(mul))
  36     return mul
  37 
  38 def foo2(**kwargs):
  39     print('Got arguments in foo1 %d %d'%( kwargs['x'] , kwargs['y']  ))
  40     mul = kwargs['x'] * kwargs['y']
  41     print('Multiplication result inside function %d'%(mul))
  42     return mul
  43 
  44 if __name__=='__main__':
  45     print( foo1(2,y=2) )
  46     print( foo2( x=3,y=3  ) )
  47     print( sys.path )
  48     print( sys.prefix )
  49     print( sys.exec_prefix )
  50     here = path.abspath(path.dirname(__file__))
  51     print(here)

   1 def add_one_args(decoratedFunction,xyz=1):
   2     def interceptor(*args, **kwargs):
   3         print "Arguments were: args %s, kwargs %s" % (args, kwargs)
   4         new_args=[]
   5 
   6         for arg in args:
   7             if isinstance(arg,int): new_args.append(arg+1)
   8             else: new_args.append(arg)
   9 
  10         args=tuple(new_args)
  11         decoratedFuncReturn = decoratedFunction(*args, **kwargs) 
  12         return decoratedFuncReturn
  13     return interceptor
  14 
  15 def subtract_one_args(decoratedFunction,xyz=1):
  16     def interceptor(*args, **kwargs):
  17         print "Arguments were: args %s, kwargs %s" % (args, kwargs)
  18         new_args=[]
  19 
  20         for arg in args:
  21             if isinstance(arg,int): new_args.append(arg-1)
  22             else: new_args.append(arg)
  23 
  24         args=tuple(new_args)
  25         decoratedFuncReturn = decoratedFunction(*args, **kwargs) 
  26         return decoratedFuncReturn
  27     return interceptor
  28 
  29 class Acme(object):
  30     def __init__(self):
  31         self.a = 0
  32         self.b = 0
  33 
  34     @add_one_args
  35     @subtract_one_args
  36     def set(self,a,b):
  37         self.a=a
  38         self.b=b
  39         print self.a, self.b
  40 
  41 if __name__=='__main__':
  42     x = Acme()
  43     x.set(0,1)

Dictionaries

   1 a={} #create dictionary
   2 if 'keyx' in a: print 'ok' #check if key keyx exists
   3 a['keyx']=1 # create key keyx with value 1
   4 if 'keyx' in a: print 'ok' #checks  keyx existence
   5 a['key2']={} # create key key2
   6 if 'keyx' in a['key2']: print 'ok' # check if keyx exists in key2
   7 a['key2']['keyx']=3 # create keyx inside key2
   8 if 'keyx' in a['key2']: print 'ok'

Exceptions

Example 1

   1 def dummyMethod(datax):
   2     try:
   3         if 'key1' in datax:
   4             key1 = datax['key1']
   5 
   6             if 'key2' in key1:
   7                 key2 = dvi['key2']
   8                 print('key2 is %s '%(key2))                    
   9 
  10     except Exception,ex:
  11         print('Error in dummyMethod %s'%( str(ex) ) )

Install pip

   1 easy_install pip

Regular expressions

   1 import re
   2 listx=['aa12.txt','a123sss.txt','bs11bb.txt','123aaaa.sql','a12.txt','aaaa12','20ghj','6657']
   3 
   4 for item in listx:
   5     res = re.match('^(\D+)(\d+)(\D+)$',item)
   6     if res!=None:
   7         decimal =  int(res.group(2)) + 1
   8         print('A: mv %s %s%d%s'%(item , res.group(1),decimal , res.group(3) ))
   9     res = re.match('^(\d+)(\D+)$',item)
  10     if res!=None:
  11         decimal =  int(res.group(1)) + 1
  12         print('B: mv %s %d%s'%(item , decimal,res.group(2)))
  13     res = re.match('^(\D+)(\d+)$',item)
  14     if res!=None:
  15         decimal =  int(res.group(2)) + 1
  16         print('C: mv %s  %s%d'%(item , res.group(1),decimal))
  17     res = re.match('^(\d+)$',item)
  18     if res!=None:
  19         decimal =  int(res.group(1)) + 1
  20         print('D: mv %s  %d'%(item , decimal))
  21 '''
  22 #ouput
  23  python addNumber.py 
  24 A: mv aa12.txt aa13.txt
  25 A: mv a123sss.txt a124sss.txt
  26 A: mv bs11bb.txt bs12bb.txt
  27 B: mv 123aaaa.sql 124aaaa.sql
  28 A: mv a12.txt a13.txt
  29 C: mv aaaa12  aaaa13
  30 B: mv 20ghj 21ghj
  31 D: mv 6657  6658
  32 '''

   1 # replace using regex (sub)
   2 import re
   3 a="adasd@gg@g:00-0:0.xml.txt"
   4 print re.sub('[@,:]','',a)
   5 # adasdggg00-00.xml.txt

Command line arguments

import sys

   1 import sys
   2 # ...
   3 if __name__=='__main__':
   4     intArgA = int(sys.argv[1])
   5     intArgB = int(sys.argv[2])
   6     intArgC = int(sys.argv[3])

Run python code in shell without source code file .py

   1 echo "<log type="typex" other="bbbbb" msgId="bbbbbb" >" | xargs -i echo -e "strx='{}'\nsplitted = strx.split(' ')\nfor spl in splitted:\n\tif 'msgId' in spl:\n\t\tprint spl.split('=')[1]"  | python

   1 strx='{}' # where xargs value is used
   2 splitted = strx.split(' ')
   3 for spl in splitted:
   4     if 'msgId' in spl:
   5         print spl.split('=')[1]

Alias identifier inside module

   1 from json import dumps as jsonDumps
   2 jsonDumps({'key':'value'})
   3 # '{"key": "value"}'
   4 print jsonDumps({'key':'value' , 'key2':1234})
   5 # {"key2": 1234, "key": "value"}

Execute process using subprocess

   1 import subprocess 
   2 
   3 if __name__=='__main__':
   4   try:
   5     args=[]
   6     args.append('ls')
   7     args.append('/tmpx')
   8     out = subprocess.check_output(args, stderr=subprocess.STDOUT, shell=False)
   9     print( out )
  10   except subprocess.CalledProcessError as ex1:
  11     print("Exception command: %s"%(ex1.cmd)  )    
  12     print("Exception code: %s"%(ex1.returncode)  )    
  13     print("Exception output: %s"%(ex1.output)  )
  14   except Exception as ex2:
  15     print("General exception %s"%(ex2.message) )

Recursion

   1 def factorial(n):
   2   if n > 0: return n * factorial(n-1)
   3   else: return 1
   4 
   5 def fibo(n):
   6   if n==0: return 0
   7   if n==1: return 1
   8   if n>1: return fibo(n-1) + fibo(n-2)
   9 
  10 def sum(idx,lista):
  11   if idx<0: return 0
  12   if idx>=0: return lista[idx] + sum(idx-1,lista)
  13 
  14 if __name__=='__main__':
  15   print( factorial(4) )
  16   print( fibo(3) )
  17   lst=[1,2,3,4]
  18   print( sum(len(lst)-1,lst) )

Python3 virtual environment

https://packaging.python.org/tutorials/installing-packages/#creating-virtual-environments

Python Virtual Environments allow Python packages to be installed in an isolated location for a particular application, rather than being installed globally.

You can deactivate a virtual environment by typing deactivate in your shell.

   1 sudo apt-get install python3-venv
   2 cd /tmp/
   3 mkdir envTest
   4 cd envTest/
   5 python3 -m venv testVenv
   6 source testVenv/bin/activate
   7 pip install --upgrade pip
   8 # pip install -i https://testpypi.python.org/pypi vbhelloworld
   9 echo -e "vbhelloworld @  https://test-files.pythonhosted.org/packages/d9/89/2ae8e276dc33d1510b8f19e4e1b2b2ca7be95ed40db89125b099609e7e1a/vbhelloworld-1.0.3.1-py2.py3-none-any.whl\n
  10 requests" > requirements.txt
  11 pip install -r requirements.txt
  12 # solve bugs in code
  13 sed -i s/yaml.load/yaml.safe_load/g testVenv/lib/python3.9/site-packages/vbhelloworld/__init__.py
  14 mkdir -p /home/vitor/.local/etc
  15 # invoke comand
  16 testVenv/bin/helloworld
  17 pip uninstall vbhelloworld
  18 deactivate

https://docs.python.org/3/library/venv.html#module-venv

When a virtual environment is active (i.e., the virtual environment’s Python interpreter is running), the attributes sys.prefix and sys.exec_prefix point to the base directory of the virtual environment, whereas sys.base_prefix and sys.base_exec_prefix point to the non-virtual environment Python installation which was used to create the virtual environment.

If a virtual environment is not active, then sys.prefix is the same as sys.base_prefix and sys.exec_prefix is the same as sys.base_exec_prefix (they all point to a non-virtual environment Python installation).

List Comprehensions

   1 squares = [x**2 for x in range(10)]
   2 # squares = [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
   3 sequence = [x for x in range(1,9)]
   4 # sequence [1, 2, 3, 4, 5, 6, 7, 8]
   5 range(10)
   6 # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
   7 squares = [x**2 for x in range(10) if x<= 4]
   8 # squares [0, 1, 4, 9, 16]

Python 2 virtual env

   1 # in windows with powershell
   2 cd ~
   3 pip install virtualenv --user
   4 # add the scripts folder to the user path c:\users\userx\AppData\Roaming\Python\Scripts 
   5 # using cmd
   6 cd %HOME_PATH%
   7 mkdir tmp
   8 cd tmp
   9 virtualenv.exe test_env
  10 cd test_env
  11 Scripts\activate.bat

   1 import sys
   2 sys.path

Generator functions yield

   1 #test yield
   2 def factorial(val):
   3     v=val
   4     res=1
   5     while v>1:
   6         res=res*v
   7         v=v-1
   8         yield None # v
   9     yield res
  10 
  11 if __name__ == "__main__":
  12     for i in factorial(3):
  13         print(i)
  14 
  15     f = factorial(4)
  16     iterate=True
  17 
  18     while iterate:
  19         try:
  20             print( f.next() )
  21             #print( next(f) )
  22         except StopIteration as ex:
  23             iterate=False

Output:

   1 python test_yeld.py 
   2 None
   3 None
   4 6
   5 None
   6 None
   7 None
   8 24

XML parse with minidom

https://docs.python.org/2/library/xml.dom.minidom.html

   1 from xml.dom import minidom
   2 print("Hello world")
   3 a="<a><b>aaaa</b><b>bbcc</b></a>"
   4 doc = minidom.parseString(a) # return document 
   5 tags = doc.getElementsByTagName("b")
   6 for t in tags:
   7   print(t.firstChild.nodeValue)

Environment variable

   1 import os
   2 print(os.environ)

XSD and objectify XML

test.py

   1 from lxml import objectify
   2 from StringIO import StringIO
   3 from lxml import etree
   4 
   5 f = open('test.xsd')
   6 xsddata=''
   7 for line in f:
   8     xsddata = xsddata +  line
   9 f.close()
  10 
  11 xmlschema_doc = etree.parse(StringIO(xsddata))
  12 xmlschema = etree.XMLSchema(xmlschema_doc)
  13 print xmlschema 
  14 
  15 parser = objectify.makeparser(schema=xmlschema)
  16 xml = "<a><b>test</b></a>"
  17 a = objectify.fromstring(xml, parser)
  18 print(a.b)

test.xsd

   1 <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
   2   <xsd:element name="a" type="AType"/>
   3   <xsd:complexType name="AType">
   4        <xsd:sequence>
   5          <xsd:element name="b" type="xsd:string" />
   6        </xsd:sequence>
   7   </xsd:complexType>
   8 </xsd:schema>

Other example ....

@startuml
class AType
class BType
class AcmeType

/' 
<|--  extends 
-- association
..> depends 
<|.. implements / realizes
'/ 

AType : b : String
AType : xx : BType
AcmeType : other : int
BType : c : String

AType ..> BType
AcmeType --|> AType
@enduml

acme.xsd

   1 <xs:schema 
   2     xmlns:xs="http://www.w3.org/2001/XMLSchema" 
   3     xmlns:bit="http://bitarus.allowed.org/types" 
   4     xmlns:ot="http://bitarus.allowed.org/othertypes" 
   5     targetNamespace="http://bitarus.allowed.org/othertypes" 
   6     elementFormDefault="qualified"
   7   >
   8   <xs:import schemaLocation="test.xsd" />  
   9   <xs:complexType name="AcmeType">  
  10     <xs:complexContent>
  11         <xs:extension base="bit:AType">
  12             <xs:sequence>
  13                 <xs:element name="other" type="xs:int"/>
  14             </xs:sequence>
  15         </xs:extension>
  16     </xs:complexContent>      
  17   </xs:complexType>
  18   <xs:element name="at" type="ot:AcmeType"/>
  19 </xs:schema>

test.xsd

   1 <xsd:schema 
   2     xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
   3     xmlns:bit="http://bitarus.allowed.org/types" 
   4     targetNamespace="http://bitarus.allowed.org/types" 
   5     elementFormDefault="qualified" 
   6 >
   7   <xsd:complexType name="AType">
   8        <xsd:sequence>
   9          <xsd:element name="b" type="xsd:string" />         
  10          <xsd:element name="xx" type="bit:BType" />
  11        </xsd:sequence>
  12   </xsd:complexType>  
  13   <xsd:complexType name="BType">
  14       <xsd:sequence>
  15         <xsd:element name="c" type="xsd:string" />
  16       </xsd:sequence>
  17   </xsd:complexType>  
  18   <xsd:element name="a" type="bit:AType"/>
  19 </xsd:schema>

acme.py

   1 from lxml import objectify
   2 from StringIO import StringIO
   3 from lxml import etree
   4 import os
   5 f = open('acme.xsd')
   6 xsddata=''
   7 for line in f:
   8     xsddata = xsddata +  line
   9 f.close()
  10 
  11 xmlschema = etree.XMLSchema(etree.parse(StringIO(xsddata)))
  12 
  13 xml = """
  14 <ot:at xmlns:ot="http://bitarus.allowed.org/othertypes" 
  15   xsi:schemaLocation="http://bitarus.allowed.org/othertypes other.xsd" 
  16   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  17   xmlns:bit="http://bitarus.allowed.org/types" >
  18   <bit:b>cccc</bit:b>
  19   <bit:xx><bit:c>hhjjkk</bit:c></bit:xx>
  20   <ot:other>1234</ot:other>  
  21 </ot:at>
  22 """
  23 
  24 doc = etree.fromstring(xml, etree.XMLParser(schema=xmlschema) )
  25 # https://lxml.de/api/lxml.etree._Element-class.html
  26 bNode = doc.getchildren()[0]
  27 otherNode = doc.getchildren()[2]
  28 print bNode.text
  29 print otherNode.text

XML tree/graph

   1 from lxml import objectify
   2 from lxml import etree
   3 from StringIO import StringIO
   4 import sys
   5 
   6 def show_children(parent,node):
   7     if node.getchildren():
   8         print parent+"/"+node.tag
   9         index=1
  10         for c in node.getchildren():
  11             show_children(parent+"/"+node.tag, c )
  12             index=index+1
  13     else:
  14         if node.text:
  15             print parent + "/"+node.tag + "=" + node.text
  16         else:
  17             print parent + "/"+node.tag
  18 
  19     if node.attrib:
  20         for key in node.attrib:
  21             print parent + "/"+node.tag +"@"+key+"="+node.attrib[key]
  22 
  23 if __name__=='__main__':
  24     f = open(sys.argv[1])
  25     data=''
  26     for line in f:
  27        if line.startswith("<?xml ")==False:  data = data +  line
  28     f.close()
  29     # print data
  30     doc = etree.fromstring( data )
  31     f.close()
  32     show_children("",doc)

Debugger

   1 # python test.py
   2 # DEBUG=on python test.py  
   3 import os
   4 # ....
   5 if 'DEBUG' in os.environ:
   6   # breakpoint 
   7   import pdb; pdb.set_trace()
   8 
   9 # commands
  10 # c continue
  11 # q quit
  12 # n next
  13 # l list
  14 # s step
  15 # w stacktrace

Remote debugger

   1 # pip install --user rpdb
   2 # cat rpdb_test.py
   3 print("aaa")
   4 # listens in 0.0.0.0 4444
   5 import rpdb; rpdb.set_trace(addr="0.0.0.0")
   6 print("bbb")
   7 print("ccc")
   8 # python3 rpdb_test.py
   9 # docker run (...) -p 4444:4444
  10 # nc localhost 4444

Install package in user home folder pointing to other libs

rpm -ql rpmpackage # check installed RPM package contents
pip install --user --global-option=build_ext --global-option="-L/usr/lib64" package_to_install

Atom syndication

Identify current function

   1 import inspect
   2 print 'In %s'%( inspect.getframeinfo(inspect.currentframe()).function )

Operative system folder path separator

   1 import os
   2 print( os.sep )
   3 help(os)
   4 dir(os)

Install package for user with a more recent version

   1 pip freeze
   2 pip install --user  numpy --upgrade
   3 pip install --user  --upgrade numpy==1.15.1
   4 pip freeze

with statement

https://www.python.org/dev/peps/pep-0343/

with EXPR as VAR:
    BLOCK
which roughly translates into this:

VAR = EXPR
VAR.__enter__()
try:
    BLOCK
finally:
    VAR.__exit__()

The open() method returns a file object. The file object has the following methods that fit in the with statement:

enter(...)
exit(...) Closes the file.

   1 with open('filex') as fx:
   2     pass

reST (ReStructuredText) docstring format

.. py:function:: send_message(sender, recipient, message_body, [priority=1])

   Send a message to a recipient

   :param str sender: The person sending the message
   :param str recipient: The recipient of the message
   :param str message_body: The body of the message
   :param priority: The priority of the message, can be a number 1-5
   :type priority: integer or None
   :return: the message id
   :rtype: int
   :raises ValueError: if the message_body exceeds 160 characters
   :raises TypeError: if the message_body is not a basestring

Static method

Adapted from https://stackoverflow.com/questions/735975/static-methods-in-python

   1 class ClassX(object):
   2     @staticmethod
   3     def static(x):
   4         print(x)
   5 
   6 ClassX.static(2) # outputs 2

Singleton

Adapted from https://www.tutorialspoint.com/python_design_patterns/python_design_patterns_singleton.htm

   1 class Singleton:
   2    __instance = None
   3 
   4    @staticmethod 
   5    def getInstance():
   6       """ Static access method. """
   7       if Singleton.__instance == None:
   8          Singleton()
   9       return Singleton.__instance
  10 
  11    def __init__(self):
  12       """ Virtually private constructor. """
  13       if Singleton.__instance != None:
  14          raise Exception("This class is a singleton!")
  15       else:
  16          Singleton.__instance = self
  17 
  18 s = Singleton()

Iterate files from a root folder

   1 #!/usr/bin/python
   2 
   3 import os
   4 for root, dirs, files in os.walk(".", topdown=False):
   5    for name in files:
   6       if name.endswith(".txt"):
   7           print(os.path.join(root, name))

xml pretty print

   1 import lxml
   2 f = open('out.xml')
   3 from lxml import etree
   4 doc = etree.fromstring( f.read() )
   5 out = etree.tostring(doc, pretty_print=True)
   6 f.close()
   7 f = open('out2.xml','wb')
   8 f.write( out ) 
   9 f.flush()
  10 f.close()
  11 quit()

docstring sphynx reST

Info field lists
New in version 0.4.
Inside Python object description directives, reST field lists with these fields are recognized and formatted nicely:
    param, parameter, arg, argument, key, keyword: Description of a parameter.
    type: Type of a parameter. Creates a link if possible.
    raises, raise, except, exception: That (and when) a specific exception is raised.
    var, ivar, cvar: Description of a variable.
    vartype: Type of a variable. Creates a link if possible.
    returns, return: Description of the return value.
    rtype: Return type. Creates a link if possible.

future

https://docs.python.org/2/library/__future__.html

   1 from __future__ import absolute_import # 3.0
   2 from __future__ import division # 3.0
   3 from __future__ import generators #2.3
   4 from __future__ import nested_scopes # 2.2
   5 from __future__ import print_function # 3.0
   6 from __future__ import unicode_literals # 3.0
   7 from __future__ import with_statement # 2.6

Command line argument parser

https://docs.python.org/2/library/argparse.html

Parser for command-line options, arguments and sub-commands

Type checking

   1 assert isinstance(obj,Class)
   2 raise NotImplementedError

Private and protected class members

   1 _member # protected member
   2 __member # private member, name mangling 
   3 member # public member

Nested class inside a function

   1 def a():
   2 
   3     class X(object):
   4         CONST=1
   5         def __init__(self):
   6             self._c = X.CONST
   7             print(self._c)
   8 
   9     x=X()
  10 
  11 if __name__=='__main__':
  12     a()

List comprehension

   1 (Pdb) [ val for val in range(1,10) if val % 2 == 0]
   2 [2, 4, 6, 8]

Change XML values with xpath

   1 from lxml import etree, objectify
   2 
   3 xml_data='<a><b><c x="as">def</c></b></a>'
   4 
   5 doc = etree.fromstring(xml_data)
   6 print "Original"
   7 print etree.tostring(doc)
   8 
   9 elem = doc.xpath('//c', namespaces=doc.nsmap)
  10 elem[0].text = "hhhhh"
  11 
  12 node_attr = doc.xpath('/a/b/c', namespaces=doc.nsmap)
  13 node_attr[0].attrib['x']='other_xyz'
  14 
  15 print etree.tostring(doc)

*args and **kwargs

   1 def x(*args,**kwargs):
   2   print type(args) # tuple
   3   print type(kwargs) # dict
   4   print args[0] # prints 1
   5   print args[1] # prints 2
   6   print kwargs['a'] # prints 1234
   7   print kwargs['b'] # prints 4567
   8 
   9 x(1 ,2, a = 1234, b = 4567)

json indentation, pretty print

   1 import json
   2 
   3 def json_to_string(obj):
   4     return json.dumps(obj,indent=4,sort_keys=True)
   5 
   6 if __name__=='__main__':
   7     print json_to_string({'a':11,'b':'fffgg'})

multiple inheritance - python 2

   1 #!/usr/local/bin/python2
   2 
   3 class A(object):
   4     def init_A(self):
   5         print("Called init_A")
   6         self.a = "aaaa"
   7 
   8     def hello(self):
   9         return "hello"
  10 
  11     def get_c(self):
  12         return self.c
  13 
  14 class C(object):
  15     def __init__(self):
  16         self.c = "cccc"
  17         print("Called init C")
  18 
  19     def world(self):
  20         return "world"
  21 
  22 class B(C, A):
  23     """Multiple inheritance from C and A """
  24     def __init__(self):
  25         super(B,self).__init__() # calls first class from which is inherited
  26         super(B,self).init_A()
  27         print(dir(self))
  28 
  29     def hello(self):
  30         return super(B,self).hello() + " " + super(B,self).world() + " " + self.c + " " + self.a
  31 
  32 if __name__=="__main__":
  33     b = B()
  34     print( b.hello() )

Output

   1 ./inheritance.py
   2 Called init C
   3 Called init_A
   4 ['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'a', 'c', 'get_c', 'hello', 'init_A', 'world']
   5 hello world cccc aaaa

globals

https://docs.python.org/3/library/functions.html#globals

Return a dictionary representing the current global symbol table.

Profiler - cProfile

profiler: identify files to review using a profiler
https://docs.python.org/2/library/profile.html ( cProfile, profile, hotshot)
python -m cProfile [-o output_file] [-s sort_order] myscript.py
python -m cProfile -o /tmp/profile.bin myscript.py

   1 import pstats
   2 import sys
   3 
   4 filename=sys.argv[1]
   5 p = pstats.Stats(filename)
   6 
   7 collection = []
   8 
   9 for stat in p.stats.values():
  10     try:
  11         mod=stat[4].keys()[0][0]
  12         item = stat[4].keys()[0][2]
  13         collection.append({"module":mod,"item":item})
  14     except:
  15         print str(stat)
  16                 
  17 for stat in p.stats.keys():
  18     try:
  19         mod=stat[0]
  20         item = stat[2]
  21         collection.append({"module":mod,"item":item})
  22     except:
  23         print str(stat)         
  24                 
  25 for element in collection:
  26     print "%s:%s"%(element['module'],element['item'])

Get current process PID

   1 import os
   2 print( os.getpid() )

AES encryption example

https://pypi.org/project/pycrypto/

   1 #crypto.py 
   2 from Crypto.Cipher import AES
   3 iv = '0123456789012345' # IV (init vector) length must be 16 
   4 key = 'Key in the house' # AES key must be either 16, 24, or 32 bytes long
   5 obj = AES.new(key, AES.MODE_CBC, iv)
   6 message = 'If u can see1234' # multiple len of 16
   7 ciphertext = obj.encrypt(message)
   8 print(ciphertext)
   9 obj2 = AES.new(key, AES.MODE_CBC, iv)
  10 decoded= obj2.decrypt(ciphertext)
  11 print(decoded)
  12 assert message == decoded

Map, filter, reduce

   1 # map_filter.py 
   2 from functools import reduce
   3 
   4 nrs = range(1,100+1)
   5 even = list( filter( lambda item: item % 2 == 0, nrs ) )
   6 print(even)
   7 
   8 nrs10 = range(1,10+1)
   9 total = reduce( (lambda a,b: a+b) , list(nrs10))
  10 print(total)
  11 
  12 multiplicationTable2 = list( map( lambda item: item*2 , nrs10 ) )
  13 print(multiplicationTable2)

Interface and Abstract classes

   1 interface_test.py 
   2 from abc import ABCMeta, abstractmethod
   3 from  math import pi
   4 
   5 class Shape(metaclass=ABCMeta):
   6     @abstractmethod
   7     def calculate_area(self):
   8         raise NotImplementedError
   9 
  10 class Square(Shape):
  11     def __init__(self,side:float):
  12         self.side = side
  13 
  14     def calculate_area(self):
  15         return self.side*self.side
  16 
  17 class Circle(Shape):
  18     def __init__(self,radius:float):
  19         self.radius = radius
  20 
  21     def calculate_area(self):
  22         return pi*self.radius*self.radius
  23 
  24 class AbsX(metaclass=ABCMeta):
  25     @abstractmethod
  26     def helloinst(self):
  27         raise NotImplementedError
  28 
  29 class X(AbsX):
  30     WORLD="world"
  31 
  32     def hello():
  33         return "hello " + X.WORLD
  34 
  35     @staticmethod
  36     def hellostatic():
  37         return "hello static " + X.WORLD
  38 
  39     def helloinst(self):
  40         return "Hello inst " + X.WORLD
  41 
  42 if __name__=='__main__':
  43     print( X.hello() )
  44     print( X.hellostatic() )
  45     print( X().helloinst() )
  46 
  47     objs = []
  48     objs.append(Square(2))
  49     objs.append(Circle(3))
  50 
  51     for o in objs:
  52         #if isinstance(o,Shape):
  53         #    print(o.calculate_area())
  54         assert( isinstance(o,Shape) )
  55         print(o.calculate_area())

-  ⇤ ← Revision 12 as of 2013-10-08 10:07:49 → 
  Size: 4103
  Editor: bl7-62-167
  Comment:
+   ← Revision 185 as of 2025-10-26 20:59:02 → ⇥
  Size: 49094
  Editor: vitor
  Comment:
-Deletions are marked like this.
+Additions are marked like this.
 Line 1:
+<<TableOfContents(2)>>
-Line 7:
+Line 8:
+ * [[https://learnxinyminutes.com/docs/python/]]
 * https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-0001-introduction-to-computer-science-and-programming-in-python-fall-2016/lecture-videos/

== Python3 ==
=== Install from SlackBuild ===
{{{#!highlight bash
cd /tmp
wget http://slackbuilds.org/slackbuilds/13.1/development/python3.tar.gz
tar xvzf python3.tar.gz
cd python3
wget http://python.org/ftp/python/3.1.3/Python-3.1.3.tar.bz2
./python3.SlackBuild
installpkg /tmp/python3-3.1.1-i486-1_SBo.tgz
}}}
-Line 17:
+Line 32:
+Letter '''ú''' is encoded  as hexadecimal '''0xC3BA''' in UTF-8, as '''0x00FA''' in UTF-16 and as '''0xFA''' in latin-1/ISO8859-1/CP-1252.

{{{#!highlight python
#utf-8 data
utf81 ='\xc3\xba' 
# convert from utf-8 to unicode
unic = utf81.decode('utf-8') 

for c in unic:
    print '%04X'%(ord(c))
# convert from unicode to latin1/ISO8859-1 CP-1252
lat1=unic.encode('latin1') 
for c in lat1:
    print '%02X'%(ord(c))
}}}

== Utf-8 and Unicode ==
{{{#!highlight python
utf81='\xe1\xb7\x97' #utf-8 data

unic = utf81.decode('utf-8') #converts from utf-8 to unicode (utf-16)
for c in unic:
    print '%04X'%(ord(c))
type(unic) # unicode, 2 bytes per char
type(utf81) # str, 1 bytes per char
}}}

{{{#!highlight python
# python3 example
a=u'cão' # string in utf-8
x=bytes(a,'utf-8') # convert string in utf-8 to bytes representation
print(dir(a))
print(dir(x))
print(type(a))
print(type(x))
b = x.decode() # convert bytes again to an utf-8 string
print(dir(b))
print(type(b))
}}}
-Line 27:
+Line 82:
+nrSeconds = time.time() #usually is UTC on all OS
-Line 33:
+Line 89:
+# timedelta
import datetime
x=datetime.datetime.fromtimestamp(1284101485)
nowx=datetime.datetime.now()                    
ts=(nowx-x).total_seconds()
print int(ts)
### add , subtract days
import datetime
x = datetime.datetime(2014,1,2)
print x
y = x - datetime.timedelta(days=1)
print y
z = y - datetime.timedelta(days=1)
print z

### convert string with date to time tuple
import time
timeTuple = time.strptime('2014-01-01 10:11:12','%Y-%m-%d %H:%M:%S')
nrSecondsSince1970=time.mktime(timeTuple)
### get seconds since epoch
start = int(datetime.datetime(2014,3,9,0,0,0,0).strftime("%s"))*1000
end = int(datetime.datetime(2014,3,14,23,59,59,999).strftime("%s"))*1000

### string from utc current date
currutc=datetime.datetime.utcnow().strftime("%Y-%m-%d %H:%M:%S")

import time
help(time.strptime)
tt=time.strptime('Sat Aug 14 20:28:54 UTC 2021','%a %b %d %H:%M:%S %Z %Y')
nrSecondsSince1970=time.mktime(tt)

# email date format
>>> time.strftime('%a, %d %b %Y %H:%M:%S %z (%Z)', time.gmtime() )
'Sun, 27 Feb 2022 14:17:14 +0000 (GMT)'
-Line 103:
+Line 193:
-== unit tests ==
{{{#!highlight python
+== unit tests (pyunit) ==
{{{#!highlight python
#filename: unitTest.py
#Run tests: python unitTest.py
#Should fail on testAdd2
-Line 107:
+Line 200:
-class SimpleWidgetTestCase(unittest.TestCase):
+class SimpleTestCase(unittest.TestCase):
-Line 109:
+Line 202:
-        self.widget = Widget('The widget')
+        self.res=4
-Line 112:
+Line 205:
-        self.widget.dispose()
        self.widget = None
+        self.res=0

    def testAdd1(self):
        res=2+2
        self.assertEqual(self.res,res,'')       

    def testAdd2(self):
        res=2+3
        self.assertEqual(self.res,res,'')       

    def testAdd3(self):
        res=2+3
        self.assertNotEqual(self.res,res,'')       

if __name__ == '__main__':
    unittest.main()
}}}

== unit tests coverage (pyunit) ==
 * http://coverage.readthedocs.io/en/latest/cmd.html
{{{#!highlight bash
pip install coverage
pip install --user --upgrade coverage 
}}}
'''tests.py'''
{{{#!highlight python
import unittest
from impl import add 
from impl import sub

class TestCase(unittest.TestCase):
    def test_add(self):
        self.assertEqual(5,add(2,3))
#    def test_sub(self):
#        self.assertEqual(1,add(3,2))
if __name__ == '__main__':
    unittest.main()
}}}

'''impl.py'''
{{{#!highlight python
def add(arg1,arg2):
    return arg1+arg2

def sub(arg1,arg2):
    return arg-+arg2
}}}

Steps:
 * coverage erase
 * coverage run tests.py
 * coverage report -m impl.py
 * coverage html impl.py  #in htmlcov folder

== unit tests - mock ==
{{{#!highlight python
from unittest.mock import MagicMock

class X(object):
    def getX(self):
        return 111

if __name__=='__main__':
    x = X()
    print(x.getX())
    x.getX = MagicMock(return_value=999)
    print( x.getX() )
-Line 117:
+Line 275:
+ * https://cython.org/
Cython is an optimising static compiler for both the Python programming language and the extended Cython programming language (based on Pyrex).
-Line 118:
+Line 279:
- * su
 * cd /tmp
 * wget http://cython.org/release/Cython-0.19.1.tar.gz
 * tar xvzf Cython-0.19.1.tar.gz 
 * cd Cython-0.19.1
 * python setup.py build
 * python setup.py install
+{{{#!highlight bash
su
cd /tmp
wget http://cython.org/release/Cython-0.19.1.tar.gz
tar xvzf Cython-0.19.1.tar.gz 
cd Cython-0.19.1
python setup.py build
python setup.py install
}}}
-Line 129:
+Line 292:
- * su
 * cd /tmp
 * wget [[http://pymssql.googlecode.com/files/pymssql-2.0.0b1-dev-20111019.tar.gz]]
 * tar xvvzf pymssql-2.0.0b1-dev-20111019.tar.gz
 * cd pymssql-2.0.0b1-dev-20111019
 * python setup.py build
 * python setup.py install
 * python
 * import pymssql
+{{{#!highlight bash
su
cd /tmp
wget [[http://pymssql.googlecode.com/files/pymssql-2.0.0b1-dev-20111019.tar.gz]]
tar xvvzf pymssql-2.0.0b1-dev-20111019.tar.gz
cd pymssql-2.0.0b1-dev-20111019
python setup.py build
python setup.py install
python
import pymssql
}}}
-Line 143:
+Line 308:
- * cd /tmp
 * hg clone https://code.google.com/p/pywhois/
 * cd pywhois
 * python setup.py build
 * python setup.py install
+{{{#!highlight bash
cd /tmp
hg clone https://code.google.com/p/pywhois/
cd pywhois
python setup.py build
python setup.py install
}}}

== Syntax highlighting on Vim for wsgi ==
Edit ~./.vimrc:
{{{#!highlight bash 
syntax on
filetype on
au BufNewFile,BufRead *.wsgi set filetype=python
}}}

== Get file modification time ==
{{{#!highlight python
import os
nrSeconds=os.path.getmtime('/folder/file') # unix epoch, nr secs since 1970-01-01 00:00:00
}}}

== Kill process with PID ==
{{{#!highlight python
import os
import signal
os.kill(pid,signal.SIGTERM) 
}}}

== Log message to /var/log/messages or /var/log/syslog ==
{{{#!highlight python
import syslog
syslog.syslog(syslog.LOG_INFO,'message to syslog')
}}}

{{{#!highlight python
import syslog

syslog.syslog(syslog.LOG_DEBUG,'DEBUG')
syslog.syslog(syslog.LOG_INFO,'INFO')
syslog.syslog(syslog.LOG_WARNING,'WARNING')
syslog.syslog(syslog.LOG_ERR,'ERR')
syslog.syslog(syslog.LOG_CRIT,'CRIT')
}}}

||OS||File||Logged levels||
||Slack64 14||/var/log/messages|| INFO ||
||Slack64 14||/var/log/syslog|| WARNING ERR CRIT ||
||CentOS 6.4||/var/log/messages|| INFO WARNING ERR CRIT ||
||Ubuntu 12.04 Precise||/var/log/syslog||DEBUG INFO WARNING ERR CRIT ||
||Debian 7.0 Wheezy||/var/log/syslog||DEBUG INFO WARNING ERR CRIT ||

== Simple process monitor ==
{{{#!highlight python
# example service, dummyService.py
import time
while True:
    try:
        f=open('filex.log','wb')
        f.write('%f'%(time.time()))
        f.close() 
        time.sleep(5)
    except KeyboardInterrupt:
        quit()
}}}

{{{#!highlight python
#service monitor.py
# * * * * * /usr/bin/python /home/vitor/svc/monitor.py
import os
import syslog
import subprocess

if __name__=="__main__":
    files = os.listdir('/proc')
    script="dummyService.py"
    prefix="dummyService:"

    svcRunning=False

    for file in files:

        if file.isdigit():
            cmdline = open('/proc/%s/cmdline'%(file),'r').read()
            proc = "%s %s "%(file,cmdline)

            if script  in proc :
                svcRunning=True

    if svcRunning==False:
        syslog.syslog(syslog.LOG_INFO,'%s process created '%(prefix) )
        # run exec process on python Popen
        subprocess.Popen(['/usr/bin/python','dummyService.py'],cwd='/home/userx/svc')
}}}

== Read URL content ==
{{{#!highlight python
import urllib2
r=urllib2.urlopen('http://www.sapo.pt')
resp=r.read()
print resp
}}}

== Windows service ==
Install http://sourceforge.net/projects/pywin32/files/pywin32/Build%20218/pywin32-218.win32-py2.5.exe/download for Python 2.5 for Windows.

Adapted from http://ryrobes.com/python/running-python-scripts-as-a-windows-service/
{{{#!highlight python
# C:\cmt\test>python testWinSvc.py install
# C:\cmt\test>python testWinSvc.py start
# C:\cmt\test>python testWinSvc.py stop
# C:\cmt\test>python testWinSvc.py remove
# C:\cmt\test>service.msc
import win32service
import win32serviceutil
import win32api
import win32con
import win32event
import win32evtlogutil
import os, sys, string, time

class aservice(win32serviceutil.ServiceFramework):
   _svc_name_ = "MyServiceShortName"
   _svc_display_name_ = "My Service Long Fancy Name!"
   _svc_description_ = "THis is what my crazy little service does - aka a DESCRIPTION! WHoa!"
         
   def __init__(self, args):
           win32serviceutil.ServiceFramework.__init__(self, args)
           self.hWaitStop = win32event.CreateEvent(None, 0, 0, None)           

   def SvcStop(self):
           self.ReportServiceStatus(win32service.SERVICE_STOP_PENDING)
           win32event.SetEvent(self.hWaitStop)                    
         
   def SvcDoRun(self):
      import servicemanager      
      servicemanager.LogMsg(servicemanager.EVENTLOG_INFORMATION_TYPE,servicemanager.PYS_SERVICE_STARTED,(self._svc_name_, ''))       
      self.timeout = 1000     #1 second
      # This is how long the service will wait to run / refresh itself (see script below)

      while 1:
         # Wait for service stop signal, if I timeout, loop again
         rc = win32event.WaitForSingleObject(self.hWaitStop, self.timeout)
         # Check to see if self.hWaitStop happened
         if rc == win32event.WAIT_OBJECT_0:
            # Stop signal encountered
            servicemanager.LogInfoMsg("SomeShortNameVersion - STOPPED!")  #For Event Log
            break
         else:
                 try:
                     handle = open('c:/windows/temp/outx1.txt', "a")
                     handle.write('%s \n' % ('tst svc'))
                     handle.close()
                 except:
                     pass



def ctrlHandler(ctrlType):
   return True
                  
if __name__ == '__main__':   
   win32api.SetConsoleCtrlHandler(ctrlHandler, True)   
   win32serviceutil.HandleCommandLine(aservice)
}}}

== Logging ==

{{{#!highlight python
import logging 
logging.basicConfig(level=logging.DEBUG,
                    format='%(asctime)s %(name)-12s %(levelname)-8s %(message)s',
                    datefmt='%m-%d %H:%M',
                    filename='/tmp/app.log',
                    filemode='w')
logging.info('Jackdaws love my big sphinx of quartz.')
logging.info('Jackdaws love my big sphinx of quartz.')
logging.info('Jackdaws love my big sphinx of quartz33.')
quit()
# cat /tmp/app.log 
}}}


Adapted from http://docs.python.org/2/howto/logging-cookbook.html#logging-to-multiple-destinations

{{{#!highlight python
import logging

logging.basicConfig(level=logging.DEBUG, \
    format='%(asctime)s %(name)-12s %(levelname)-8s %(message)s', \
    datefmt='%Y-%m-%d %H:%M:%S %z', \
    filename='/tmp/myapp.log', \
    filemode='a')
#log to console
console = logging.StreamHandler()
console.setLevel(logging.INFO)
formatter = logging.Formatter('%(name)-12s: %(levelname)-8s %(message)s')
console.setFormatter(formatter)
logging.getLogger('').addHandler(console)
logging.info('Jackdaws love my big sphinx of quartz.') # using default logger '' 
#other loggers
logger1 = logging.getLogger('myapp.area1')
logger2 = logging.getLogger(__name__)
logger1.debug('Quick zephyrs blow, vexing daft Jim.')
logger1.info('How quickly daft jumping zebras vex.')
logger2.warning('Jail zesty vixen who grabbed pay from quack.')
logger2.error('The five boxing wizards jump quickly.')
}}}


Copied from http://docs.python.org/2/howto/logging-cookbook.html#configuration-server-example
Logging configurable on runtime, receiving new parameters by socket

Server:
{{{#!highlight python
import logging
import logging.config
import time
import os

# read initial config file
logging.config.fileConfig('logging.conf')

# create and start listener on port 9999
t = logging.config.listen(9999)
t.start()

logger = logging.getLogger('simpleExample')

try:
    # loop through logging calls to see the difference
    # new configurations make, until Ctrl+C is pressed
    while True:
        logger.debug('debug message')
        logger.info('info message')
        logger.warn('warn message')
        logger.error('error message')
        logger.critical('critical message')
        time.sleep(5)
except KeyboardInterrupt:
    # cleanup
    logging.config.stopListening()
    t.join()
}}}

Client:
{{{#!highlight python
#!/usr/bin/env python
import socket, sys, struct

with open(sys.argv[1], 'rb') as f:
    data_to_send = f.read()

HOST = 'localhost'
PORT = 9999
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print('connecting...')
s.connect((HOST, PORT))
print('sending config...')
s.send(struct.pack('>L', len(data_to_send)))
s.send(data_to_send)
s.close()
print('complete')
}}}

== Logging with date rotation and email ==
{{{#!highlight python
import logging
from logging.handlers import TimedRotatingFileHandler
from logging.handlers import SMTPHandler

class Logger(object):
    def __init__(self):
        loggerName='appx'
        logFormatter = logging.Formatter('[%(asctime)s %(name)-12s %(levelname)-8s] %(message)s',datefmt='%Y-%m-%d %H:%M:%S %z')
        
        rotatingLogHandler = TimedRotatingFileHandler('%s.log'%(loggerName),when='midnight',utc=True)
        rotatingLogHandler.setFormatter(logFormatter)
        rotatingLogHandler.setLevel(logging.DEBUG)

        smtpLogHandler = SMTPHandler(mailhost='hostx.com', fromaddr='mail@hostx.com', toaddrs='dest@hostx.com', subject=loggerName, \
            credentials=('accountx','12345678'), secure=None)
        smtpLogHandler.setFormatter(logFormatter)
        smtpLogHandler.setLevel(logging.WARNING)
                        
        self.logger = logging.getLogger(loggerName)
        self.logger.addHandler(rotatingLogHandler)
        self.logger.addHandler(smtpLogHandler)
        self.logger.setLevel(logging.DEBUG)
        
    def debug(self,m):
        self.logger.debug(m)

    def info(self,m):
        self.logger.info(m)

    def warning(self,m):
        self.logger.warning(m)
        
    def error(self,m):
        self.logger.error(m)
        
    def critical(self,m):
        self.logger.critical(m)

}}}

== pytz - World Timezone Definitions for Python ==
{{{#!highlight python

import pytz
import datetime

#fmt = '%Y-%m-%d %H:%M:%S %Z%z'
london=pytz.timezone('Europe/London')
lisbon=pytz.timezone('Europe/Lisbon')
paris  =pytz.timezone('Europe/Paris')
utc = pytz.timezone('UTC')
berlin = pytz.timezone('Europe/Berlin')

print
dtx = datetime.datetime(2002, 12, 27, 12, 0, 0,tzinfo=utc ) 
print 
print 'UTC    ' , dtx
print 'London ',dtx.astimezone(london)
print 'Lisbon ',dtx.astimezone(lisbon)
print 'Paris  ',dtx.astimezone(paris)
print 'Berlin ',dtx.astimezone(berlin)


print
dty = datetime.datetime(2002, 8, 27, 13, 0, 0,tzinfo=utc ) 
print 'UTC    ',dty
print 'London ',dty.astimezone(london)
print 'Lisbon ',dty.astimezone(lisbon)
print 'Paris  ',dty.astimezone(paris)
print 'Berlin ',dty.astimezone(berlin)
}}}

== Sort example ==
{{{#!highlight python
class Acme(object):
    def __init__(self,valuex):
        self.valuex=valuex

    def __cmp__(self, other):
        if self.valuex==other.valuex:
            return 0
        if self.valuex>other.valuex:
            return 1
        if self.valuex<other.valuex:
            return -1

    def __repr__(self):
        return self.valuex

if __name__=='__main__':
    listx=[]
    listx.append( Acme('C') )
    listx.append( Acme('A') )
    listx.append( Acme('Z') )
    print 'original:',listx
    print 'sorted asc:',sorted(listx,reverse=False)
    print 'sorted desc:',sorted(listx,reverse=True)
    listx.sort()
    print 'sort:',listx
    listx.reverse()
    print 'reverse:',listx
}}}

== sys.path ==
With sys.path we are able to add new folders which serve as base path to modules. The idea is similar to classpath in Java.

Create file /tmp/testex.py
{{{#!highlight python
def test1()
    print("Alright !!!!")
}}}

Run python interactively:
{{{#!highlight bash
vitor@darkstar[~]$python
Python 2.7.3 (default, Jul  3 2012, 21:16:07) 
[GCC 4.7.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import testex
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named testex
>>> import sys
>>> sys.path.append('/tmp') # add /tmp to modules paths
>>> testex.test1()
Allright !!!!
}}}

By default on Linux systems, modules are also searched in '''~/.local/pythonXX.YY/site-packages'''. If the file testex.py would exist, it would also be used without being necessary to add the folder /tmp to the '''sys.path''' . For the user vitor and python 2.7 the path would be '''/home/vitor/.local/lib/python2.7/site-packages''' .

== Math ==
{{{#!highlight python
# round float to 6 decimal places
nr=1.23456789
print round(nr,6)
# round float to 4 decimal places
nr=1.23456789
print round(nr,4)
}}}

== SMTP ==
{{{#!highlight python
import smtplib

class Smtp(object):
    def __init__(self,server,port,user,passx,appName):
        self.server=server
        self.port=port
        self.user=user
        self.passx=passx
        self.appName=appName

    def send(self,fromx,tox,subjectx,contentType,body):
        s=smtplib.SMTP()
        s.connect(self.server,self.port)
        s.ehlo(self.appName)
        s.login(self.user,self.passx)         
        msg='From: %s\r\nTo: %s\r\nSubject: %s\r\nContent-Type: %s\r\n\r\n%s'%(fromx,tox,subjectx,contentType,body)
        s.sendmail(fromx,tox,msg)
        s.quit()

s=Smtp('mail.example.org',25,'norep@example.org','12345678','TestApp')
# content types: text/plain text/html
s.send('norep@example.org',['user1@example.org','user2@example.org'],'Subject','text/plain','Body mail')
}}}

== JSON serializable ==
{{{#!highlight python
from json import JSONEncoder
import json

class EncoderJSON(JSONEncoder):
    def default(self, o):
        return o.getJSONDict()    
    
class Acme(object):
    def __init__(self,paramx,valuex):
        self.paramx=paramx
        self.valuex=valuex
        
    def getJSONDict(self):
        return {'paramx':self.paramx ,'valuex':self.valuex}
                
    def __repr__(self):
        return '%s %s %s'%(self.paramx ,self.valuex)

if __name__=='__main__':
    listx=[]
    listx.append(Acme('p1','v1'))
    listx.append(Acme('p2','v2'))
    # json.dumps likes lists and dictionaries
    print( json.dumps(listx,cls=EncoderJSON) ) 
    # output [{"valuex": "v1", "paramx": "p1"}, {"valuex": "v2", "paramx": "p2"}]

}}}

== Decorators ==
http://simeonfranklin.com/blog/2012/jul/1/python-decorators-in-12-steps/

Wraps functions with functionality, before, after , changes parameters of the decorated function.

{{{#!highlight python
#decorator logger
def logger(func):
        def inner(*args, **kwargs): # step 1
            print "Arguments were: %s, %s" % (args, kwargs)
            return func(*args, **kwargs) # step 2
        return inner

@logger
def foo1(x, y=1):
    return x * y
if __name__=='__main__':
    foo1(2,2)
}}}

{{{#!highlight python
import sys
from os import path 
#decorator adder
def add_one_args(decoratedFunction):
    def interceptor(*args, **kwargs): # step 1
        print "Arguments were: args %s, kwargs %s" % (args, kwargs)
        index=0
        new_args=[]
        # change input 
        isnotint=False
        for arg in args:
            if isinstance(arg,int):                    
                new_args.append(arg+1)
            else:
                isnotint=True
            index=index+1
                
        if isnotint==False: 
            args=tuple(new_args)

        new_kwargs={}
        for kwarg in kwargs:
            new_kwargs[kwarg] = kwargs[kwarg]+1

        decoratedFuncReturn =  decoratedFunction(*args, **new_kwargs) # step 2
        # change output
        decoratedFuncReturn = decoratedFuncReturn * 2
        return decoratedFuncReturn
    return interceptor

@add_one_args
def foo1(x, y=1):
    print('Got arguments in foo1 %d %d'%(x,y))
    mul = x * y
    print('Multiplication result inside function %d'%(mul))
    return mul

def foo2(**kwargs):
    print('Got arguments in foo1 %d %d'%( kwargs['x'] , kwargs['y']  ))
    mul = kwargs['x'] * kwargs['y']
    print('Multiplication result inside function %d'%(mul))
    return mul

if __name__=='__main__':
    print( foo1(2,y=2) )
    print( foo2( x=3,y=3  ) )
    print( sys.path )
    print( sys.prefix )
    print( sys.exec_prefix )
    here = path.abspath(path.dirname(__file__))
    print(here)
}}}

{{{#!highlight python
def add_one_args(decoratedFunction,xyz=1):
    def interceptor(*args, **kwargs):
        print "Arguments were: args %s, kwargs %s" % (args, kwargs)
        new_args=[]

        for arg in args:
            if isinstance(arg,int): new_args.append(arg+1)
            else: new_args.append(arg)

        args=tuple(new_args)
        decoratedFuncReturn = decoratedFunction(*args, **kwargs) 
        return decoratedFuncReturn
    return interceptor

def subtract_one_args(decoratedFunction,xyz=1):
    def interceptor(*args, **kwargs):
        print "Arguments were: args %s, kwargs %s" % (args, kwargs)
        new_args=[]

        for arg in args:
            if isinstance(arg,int): new_args.append(arg-1)
            else: new_args.append(arg)

        args=tuple(new_args)
        decoratedFuncReturn = decoratedFunction(*args, **kwargs) 
        return decoratedFuncReturn
    return interceptor

class Acme(object):
    def __init__(self):
        self.a = 0
        self.b = 0

    @add_one_args
    @subtract_one_args
    def set(self,a,b):
        self.a=a
        self.b=b
        print self.a, self.b

if __name__=='__main__':
    x = Acme()
    x.set(0,1)
}}}


== Dictionaries ==
{{{#!highlight python
a={} #create dictionary
if 'keyx' in a: print 'ok' #check if key keyx exists
a['keyx']=1 # create key keyx with value 1
if 'keyx' in a: print 'ok' #checks  keyx existence
a['key2']={} # create key key2
if 'keyx' in a['key2']: print 'ok' # check if keyx exists in key2
a['key2']['keyx']=3 # create keyx inside key2
if 'keyx' in a['key2']: print 'ok'
}}}

== Exceptions ==
Example 1
{{{#!highlight python
def dummyMethod(datax):
    try:
        if 'key1' in datax:
            key1 = datax['key1']

            if 'key2' in key1:
                key2 = dvi['key2']
                print('key2 is %s '%(key2))                    

    except Exception,ex:
        print('Error in dummyMethod %s'%( str(ex) ) )
}}}

== Install pip ==
{{{#!highlight bash
easy_install pip
}}}

== Regular expressions ==
{{{#!python
import re
listx=['aa12.txt','a123sss.txt','bs11bb.txt','123aaaa.sql','a12.txt','aaaa12','20ghj','6657']

for item in listx:
    res = re.match('^(\D+)(\d+)(\D+)$',item)
    if res!=None:
        decimal =  int(res.group(2)) + 1
        print('A: mv %s %s%d%s'%(item , res.group(1),decimal , res.group(3) ))
    res = re.match('^(\d+)(\D+)$',item)
    if res!=None:
        decimal =  int(res.group(1)) + 1
        print('B: mv %s %d%s'%(item , decimal,res.group(2)))
    res = re.match('^(\D+)(\d+)$',item)
    if res!=None:
        decimal =  int(res.group(2)) + 1
        print('C: mv %s  %s%d'%(item , res.group(1),decimal))
    res = re.match('^(\d+)$',item)
    if res!=None:
        decimal =  int(res.group(1)) + 1
        print('D: mv %s  %d'%(item , decimal))
'''
#ouput
 python addNumber.py 
A: mv aa12.txt aa13.txt
A: mv a123sss.txt a124sss.txt
A: mv bs11bb.txt bs12bb.txt
B: mv 123aaaa.sql 124aaaa.sql
A: mv a12.txt a13.txt
C: mv aaaa12  aaaa13
B: mv 20ghj 21ghj
D: mv 6657  6658
'''
}}}

{{{#!highlight python
# replace using regex (sub)
import re
a="adasd@gg@g:00-0:0.xml.txt"
print re.sub('[@,:]','',a)
# adasdggg00-00.xml.txt
}}}

== Command line arguments ==
 * import sys
{{{#!highlight python
import sys
# ...
if __name__=='__main__':
    intArgA = int(sys.argv[1])
    intArgB = int(sys.argv[2])
    intArgC = int(sys.argv[3])

}}}

== Run python code in shell without source code file .py ==
{{{#!highlight sh
echo "<log type="typex" other="bbbbb" msgId="bbbbbb" >" | xargs -i echo -e "strx='{}'\nsplitted = strx.split(' ')\nfor spl in splitted:\n\tif 'msgId' in spl:\n\t\tprint spl.split('=')[1]"  | python                         
}}}

{{{#!highlight python
strx='{}' # where xargs value is used
splitted = strx.split(' ')
for spl in splitted:
    if 'msgId' in spl:
        print spl.split('=')[1]
}}}

== Alias identifier inside module ==
{{{#!highlight python
from json import dumps as jsonDumps
jsonDumps({'key':'value'})
# '{"key": "value"}'
print jsonDumps({'key':'value' , 'key2':1234})
# {"key2": 1234, "key": "value"} 
}}}

== Execute process using subprocess ==
{{{#!highlight python
import subprocess 

if __name__=='__main__':
  try:
    args=[]
    args.append('ls')
    args.append('/tmpx')
    out = subprocess.check_output(args, stderr=subprocess.STDOUT, shell=False)
    print( out )
  except subprocess.CalledProcessError as ex1:
    print("Exception command: %s"%(ex1.cmd)  )    
    print("Exception code: %s"%(ex1.returncode)  )    
    print("Exception output: %s"%(ex1.output)  )
  except Exception as ex2:
    print("General exception %s"%(ex2.message) )    
}}}

== Recursion ==
{{{#!highlight python   
def factorial(n):
  if n > 0: return n * factorial(n-1)
  else: return 1

def fibo(n):
  if n==0: return 0
  if n==1: return 1
  if n>1: return fibo(n-1) + fibo(n-2)

def sum(idx,lista):
  if idx<0: return 0
  if idx>=0: return lista[idx] + sum(idx-1,lista)

if __name__=='__main__':
  print( factorial(4) )
  print( fibo(3) )
  lst=[1,2,3,4]
  print( sum(len(lst)-1,lst) )
}}}

== Python3 virtual environment ==
 * https://packaging.python.org/tutorials/installing-packages/#creating-virtual-environments

Python '''Virtual Environments''' allow Python packages to be installed in an isolated location for a particular application, rather than being installed globally.

You can deactivate a virtual environment by typing '''deactivate''' in your shell.

{{{#!highlight bash
sudo apt-get install python3-venv
cd /tmp/
mkdir envTest
cd envTest/
python3 -m venv testVenv
source testVenv/bin/activate
pip install --upgrade pip
# pip install -i https://testpypi.python.org/pypi vbhelloworld
echo -e "vbhelloworld @  https://test-files.pythonhosted.org/packages/d9/89/2ae8e276dc33d1510b8f19e4e1b2b2ca7be95ed40db89125b099609e7e1a/vbhelloworld-1.0.3.1-py2.py3-none-any.whl\n
requests" > requirements.txt
pip install -r requirements.txt
# solve bugs in code
sed -i s/yaml.load/yaml.safe_load/g testVenv/lib/python3.9/site-packages/vbhelloworld/__init__.py
mkdir -p /home/vitor/.local/etc
# invoke comand
testVenv/bin/helloworld
pip uninstall vbhelloworld
deactivate
}}}

 * https://docs.python.org/3/library/venv.html#module-venv

When a virtual environment is active (i.e., the virtual environment’s Python interpreter is running), the attributes sys.prefix and sys.exec_prefix point to the base directory of the virtual environment, whereas sys.base_prefix and sys.base_exec_prefix point to the non-virtual environment Python installation which was used to create the virtual environment. 

If a virtual environment is not active, then sys.prefix is the same as sys.base_prefix and sys.exec_prefix is the same as sys.base_exec_prefix (they all point to a non-virtual environment Python installation).

== List Comprehensions ==
{{{#!highlight python
squares = [x**2 for x in range(10)]
# squares = [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
sequence = [x for x in range(1,9)]
# sequence [1, 2, 3, 4, 5, 6, 7, 8]
range(10)
# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
squares = [x**2 for x in range(10) if x<= 4]
# squares [0, 1, 4, 9, 16]
}}}

== Python 2 virtual env ==
{{{#!highlight sh
# in windows with powershell
cd ~
pip install virtualenv --user
# add the scripts folder to the user path c:\users\userx\AppData\Roaming\Python\Scripts 
# using cmd
cd %HOME_PATH%
mkdir tmp
cd tmp
virtualenv.exe test_env
cd test_env
Scripts\activate.bat
}}}

{{{#!highlight python
import sys
sys.path
}}}

== Generator functions yield ==
{{{#!highlight python
#test yield
def factorial(val):
    v=val
    res=1
    while v>1:
        res=res*v
        v=v-1
        yield None # v
    yield res

if __name__ == "__main__":
    for i in factorial(3):
        print(i)

    f = factorial(4)
    iterate=True

    while iterate:
        try:
            print( f.next() )
            #print( next(f) )
        except StopIteration as ex:
            iterate=False
}}}

'''Output:'''
{{{#!highlight bash
python test_yeld.py 
None
None
6
None
None
None
24
}}}

== XML parse with minidom ==
 * https://docs.python.org/2/library/xml.dom.minidom.html
{{{#!highlight python
from xml.dom import minidom
print("Hello world")
a="<a><b>aaaa</b><b>bbcc</b></a>"
doc = minidom.parseString(a) # return document 
tags = doc.getElementsByTagName("b")
for t in tags:
  print(t.firstChild.nodeValue)

}}}

== Environment variable ==
{{{#!highlight python
import os
print(os.environ)
}}}


== XSD and objectify XML ==
'''test.py'''
{{{#!highlight python
from lxml import objectify
from StringIO import StringIO
from lxml import etree

f = open('test.xsd')
xsddata=''
for line in f:
    xsddata = xsddata +  line
f.close()

xmlschema_doc = etree.parse(StringIO(xsddata))
xmlschema = etree.XMLSchema(xmlschema_doc)
print xmlschema 

parser = objectify.makeparser(schema=xmlschema)
xml = "<a><b>test</b></a>"
a = objectify.fromstring(xml, parser)
print(a.b)
}}}

'''test.xsd'''
{{{#!highlight xml
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <xsd:element name="a" type="AType"/>
  <xsd:complexType name="AType">
       <xsd:sequence>
         <xsd:element name="b" type="xsd:string" />
       </xsd:sequence>
  </xsd:complexType>
</xsd:schema>
}}}

'''Other example ....'''
{{{
@startuml
class AType
class BType
class AcmeType

/' 
<|--  extends 
-- association
..> depends 
<|.. implements / realizes
'/ 

AType : b : String
AType : xx : BType
AcmeType : other : int
BType : c : String

AType ..> BType
AcmeType --|> AType
@enduml
}}}

{{attachment:classes.png}}

'''acme.xsd'''
{{{#!highlight xml
<xs:schema 
    xmlns:xs="http://www.w3.org/2001/XMLSchema" 
    xmlns:bit="http://bitarus.allowed.org/types" 
    xmlns:ot="http://bitarus.allowed.org/othertypes" 
    targetNamespace="http://bitarus.allowed.org/othertypes" 
    elementFormDefault="qualified"
  >
  <xs:import schemaLocation="test.xsd" />  
  <xs:complexType name="AcmeType">  
    <xs:complexContent>
        <xs:extension base="bit:AType">
            <xs:sequence>
                <xs:element name="other" type="xs:int"/>
            </xs:sequence>
        </xs:extension>
    </xs:complexContent>      
  </xs:complexType>
  <xs:element name="at" type="ot:AcmeType"/>
</xs:schema>
}}}

'''test.xsd'''
{{{#!highlight xml
<xsd:schema 
    xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
    xmlns:bit="http://bitarus.allowed.org/types" 
    targetNamespace="http://bitarus.allowed.org/types" 
    elementFormDefault="qualified" 
>
  <xsd:complexType name="AType">
       <xsd:sequence>
         <xsd:element name="b" type="xsd:string" />         
         <xsd:element name="xx" type="bit:BType" />
       </xsd:sequence>
  </xsd:complexType>  
  <xsd:complexType name="BType">
      <xsd:sequence>
        <xsd:element name="c" type="xsd:string" />
      </xsd:sequence>
  </xsd:complexType>  
  <xsd:element name="a" type="bit:AType"/>
</xsd:schema>
}}}

'''acme.py'''
{{{#!highlight python
from lxml import objectify
from StringIO import StringIO
from lxml import etree
import os
f = open('acme.xsd')
xsddata=''
for line in f:
    xsddata = xsddata +  line
f.close()

xmlschema = etree.XMLSchema(etree.parse(StringIO(xsddata)))

xml = """
<ot:at xmlns:ot="http://bitarus.allowed.org/othertypes" 
  xsi:schemaLocation="http://bitarus.allowed.org/othertypes other.xsd" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:bit="http://bitarus.allowed.org/types" >
  <bit:b>cccc</bit:b>
  <bit:xx><bit:c>hhjjkk</bit:c></bit:xx>
  <ot:other>1234</ot:other>  
</ot:at>
"""

doc = etree.fromstring(xml, etree.XMLParser(schema=xmlschema) )
# https://lxml.de/api/lxml.etree._Element-class.html
bNode = doc.getchildren()[0]
otherNode = doc.getchildren()[2]
print bNode.text
print otherNode.text
}}}

== XML tree/graph ==
{{{#!highlight python
from lxml import objectify
from lxml import etree
from StringIO import StringIO
import sys

def show_children(parent,node):
    if node.getchildren():
        print parent+"/"+node.tag
        index=1
        for c in node.getchildren():
            show_children(parent+"/"+node.tag, c )
            index=index+1
    else:
        if node.text:
            print parent + "/"+node.tag + "=" + node.text
        else:
            print parent + "/"+node.tag

    if node.attrib:
        for key in node.attrib:
            print parent + "/"+node.tag +"@"+key+"="+node.attrib[key]

if __name__=='__main__':
    f = open(sys.argv[1])
    data=''
    for line in f:
       if line.startswith("<?xml ")==False:  data = data +  line
    f.close()
    # print data
    doc = etree.fromstring( data )
    f.close()
    show_children("",doc)
}}}

== Debugger ==
{{{#!highlight python
# python test.py
# DEBUG=on python test.py  
import os
# ....
if 'DEBUG' in os.environ:
  # breakpoint 
  import pdb; pdb.set_trace()

# commands
# c continue
# q quit
# n next
# l list
# s step
# w stacktrace
}}}

== Remote debugger ==
{{{#!highlight python
# pip install --user rpdb
# cat rpdb_test.py
print("aaa")
# listens in 0.0.0.0 4444
import rpdb; rpdb.set_trace(addr="0.0.0.0")
print("bbb")
print("ccc")
# python3 rpdb_test.py
# docker run (...) -p 4444:4444
# nc localhost 4444
}}}

== Install package in user home folder pointing to other libs ==
 * rpm -ql rpmpackage # check installed RPM package contents
 * pip install  --user --global-option=build_ext --global-option="-L/usr/lib64" package_to_install

== Atom syndication ==
 * https://tools.ietf.org/html/rfc4287
 * https://www.iana.org/assignments/xml-registry/schema/vcard-4.0.xsd 
 * https://www.iana.org/assignments/xml-registry/xml-registry.xhtml

== Identify current function ==
{{{#!highlight python
import inspect
print 'In %s'%( inspect.getframeinfo(inspect.currentframe()).function )
}}}

== Operative system folder path separator ==
{{{#!highlight python
import os
print( os.sep )
help(os)
dir(os)
}}}

== Install package for user with a more recent version ==
{{{#!highlight bash
pip freeze
pip install --user  numpy --upgrade
pip install --user  --upgrade numpy==1.15.1
pip freeze
}}}

== with statement ==
 * https://www.python.org/dev/peps/pep-0343/

{{{
with EXPR as VAR:
    BLOCK
which roughly translates into this:

VAR = EXPR
VAR.__enter__()
try:
    BLOCK
finally:
    VAR.__exit__()
}}}

The open() method returns a file object. The file object has the following methods that fit in the with statement:
 * __enter__(...)
 * __exit__(...)  Closes the file.

{{{#!highlight python
with open('filex') as fx:
    pass
}}}

== reST (ReStructuredText) docstring format ==
 * https://pythonhosted.org/an_example_pypi_project/sphinx.html#restructured-text-rest-resources
 * http://www.sphinx-doc.org/en/1.6/domains.html#the-python-domain
{{{
.. py:function:: send_message(sender, recipient, message_body, [priority=1])

   Send a message to a recipient

   :param str sender: The person sending the message
   :param str recipient: The recipient of the message
   :param str message_body: The body of the message
   :param priority: The priority of the message, can be a number 1-5
   :type priority: integer or None
   :return: the message id
   :rtype: int
   :raises ValueError: if the message_body exceeds 160 characters
   :raises TypeError: if the message_body is not a basestring
}}}

== Static method ==
Adapted from https://stackoverflow.com/questions/735975/static-methods-in-python

{{{#!highlight python
class ClassX(object):
    @staticmethod
    def static(x):
        print(x)

ClassX.static(2) # outputs 2
}}}

== Singleton ==
Adapted from https://www.tutorialspoint.com/python_design_patterns/python_design_patterns_singleton.htm
{{{#!highlight python
class Singleton:
   __instance = None

   @staticmethod 
   def getInstance():
      """ Static access method. """
      if Singleton.__instance == None:
         Singleton()
      return Singleton.__instance

   def __init__(self):
      """ Virtually private constructor. """
      if Singleton.__instance != None:
         raise Exception("This class is a singleton!")
      else:
         Singleton.__instance = self

s = Singleton()
}}}

== Iterate files from a root folder ==
{{{#!highlight python
#!/usr/bin/python

import os
for root, dirs, files in os.walk(".", topdown=False):
   for name in files:
      if name.endswith(".txt"):
          print(os.path.join(root, name))
}}}

== xml pretty print ==
{{{#!highlight python
import lxml
f = open('out.xml')
from lxml import etree
doc = etree.fromstring( f.read() )
out = etree.tostring(doc, pretty_print=True)
f.close()
f = open('out2.xml','wb')
f.write( out ) 
f.flush()
f.close()
quit()
}}}

== docstring sphynx reST ==
 * https://www.sphinx-doc.org/en/master/usage/restructuredtext/domains.html
 * https://www.sphinx-doc.org/en/master/usage/restructuredtext/domains.html?highlight=param#the-python-domain
 * https://www.sphinx-doc.org/en/master/usage/restructuredtext/domains.html?highlight=param#info-field-lists
{{{
Info field lists
New in version 0.4.
Inside Python object description directives, reST field lists with these fields are recognized and formatted nicely:
    param, parameter, arg, argument, key, keyword: Description of a parameter.
    type: Type of a parameter. Creates a link if possible.
    raises, raise, except, exception: That (and when) a specific exception is raised.
    var, ivar, cvar: Description of a variable.
    vartype: Type of a variable. Creates a link if possible.
    returns, return: Description of the return value.
    rtype: Return type. Creates a link if possible.
}}}

== __future__ ==
 * https://docs.python.org/2/library/__future__.html
{{{#!highlight python
from __future__ import absolute_import # 3.0
from __future__ import division # 3.0
from __future__ import generators #2.3
from __future__ import nested_scopes # 2.2
from __future__ import print_function # 3.0
from __future__ import unicode_literals # 3.0
from __future__ import with_statement # 2.6
}}}

== Command line argument parser ==
 * https://docs.python.org/2/library/argparse.html
Parser for command-line options, arguments and sub-commands

== Type checking ==
{{{#!highlight python
assert isinstance(obj,Class)
raise NotImplementedError
}}}

== Private and protected class members ==
{{{#!highlight python
_member # protected member
__member # private member, name mangling 
member # public member
}}}

== Nested class inside a function ==
{{{#!highlight python
def a():

    class X(object):
        CONST=1
        def __init__(self):
            self._c = X.CONST
            print(self._c)

    x=X()

if __name__=='__main__':
    a()
}}}

== List comprehension ==
{{{#!highlight python
(Pdb) [ val for val in range(1,10) if val % 2 == 0]
[2, 4, 6, 8]
}}}

== Change XML values with xpath ==
{{{#!highlight python
from lxml import etree, objectify

xml_data='<a><b><c x="as">def</c></b></a>'

doc = etree.fromstring(xml_data)
print "Original"
print etree.tostring(doc)

elem = doc.xpath('//c', namespaces=doc.nsmap)
elem[0].text = "hhhhh"

node_attr = doc.xpath('/a/b/c', namespaces=doc.nsmap)
node_attr[0].attrib['x']='other_xyz'

print etree.tostring(doc)
}}}

== *args and **kwargs ==
{{{#!highlight python
def x(*args,**kwargs):
  print type(args) # tuple
  print type(kwargs) # dict
  print args[0] # prints 1
  print args[1] # prints 2
  print kwargs['a'] # prints 1234
  print kwargs['b'] # prints 4567

x(1 ,2, a = 1234, b = 4567)
}}}


== json indentation, pretty print ==
{{{#!highlight python
import json

def json_to_string(obj):
    return json.dumps(obj,indent=4,sort_keys=True)

if __name__=='__main__':
    print json_to_string({'a':11,'b':'fffgg'})
}}}

== multiple inheritance - python 2 ==
{{{#!highlight python
#!/usr/local/bin/python2

class A(object):
    def init_A(self):
        print("Called init_A")
        self.a = "aaaa"

    def hello(self):
        return "hello"

    def get_c(self):
        return self.c

class C(object):
    def __init__(self):
        self.c = "cccc"
        print("Called init C")

    def world(self):
        return "world"

class B(C, A):
    """Multiple inheritance from C and A """
    def __init__(self):
        super(B,self).__init__() # calls first class from which is inherited
        super(B,self).init_A()
        print(dir(self))

    def hello(self):
        return super(B,self).hello() + " " + super(B,self).world() + " " + self.c + " " + self.a

if __name__=="__main__":
    b = B()
    print( b.hello() )
}}}

Output
{{{#!highlight sh
./inheritance.py
Called init C
Called init_A
['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'a', 'c', 'get_c', 'hello', 'init_A', 'world']
hello world cccc aaaa
}}}


== globals ==
 * https://docs.python.org/3/library/functions.html#globals
Return a dictionary representing the current global symbol table. 

== Profiler - cProfile ==
 * profiler: identify files to review using a profiler
 * https://docs.python.org/2/library/profile.html ( cProfile, profile, hotshot)
 * python -m cProfile [-o output_file] [-s sort_order] myscript.py
 * python -m cProfile -o /tmp/profile.bin myscript.py

{{{#!highlight python
import pstats
import sys

filename=sys.argv[1]
p = pstats.Stats(filename)

collection = []

for stat in p.stats.values():
    try:
        mod=stat[4].keys()[0][0]
        item = stat[4].keys()[0][2]
        collection.append({"module":mod,"item":item})
    except:
        print str(stat)
  
for stat in p.stats.keys():
    try:
        mod=stat[0]
        item = stat[2]
        collection.append({"module":mod,"item":item})
    except:
        print str(stat)		
  
for element in collection:
    print "%s:%s"%(element['module'],element['item'])		

}}}

== Get current process PID ==
{{{#!highlight python
import os
print( os.getpid() )
}}}

== AES encryption example ==
 * https://pypi.org/project/pycrypto/
{{{#!highlight python
#crypto.py 
from Crypto.Cipher import AES
iv = '0123456789012345' # IV (init vector) length must be 16 
key = 'Key in the house' # AES key must be either 16, 24, or 32 bytes long
obj = AES.new(key, AES.MODE_CBC, iv)
message = 'If u can see1234' # multiple len of 16
ciphertext = obj.encrypt(message)
print(ciphertext)
obj2 = AES.new(key, AES.MODE_CBC, iv)
decoded= obj2.decrypt(ciphertext)
print(decoded)
assert message == decoded
}}}

== Map, filter, reduce ==
{{{#!highlight python3
# map_filter.py 
from functools import reduce

nrs = range(1,100+1)
even = list( filter( lambda item: item % 2 == 0, nrs ) )
print(even)

nrs10 = range(1,10+1)
total = reduce( (lambda a,b: a+b) , list(nrs10))
print(total)

multiplicationTable2 = list( map( lambda item: item*2 , nrs10 ) )
print(multiplicationTable2)
}}}


== Interface and Abstract classes ==
{{{#!highlight python
interface_test.py 
from abc import ABCMeta, abstractmethod
from  math import pi

class Shape(metaclass=ABCMeta):
    @abstractmethod
    def calculate_area(self):
        raise NotImplementedError

class Square(Shape):
    def __init__(self,side:float):
        self.side = side

    def calculate_area(self):
        return self.side*self.side

class Circle(Shape):
    def __init__(self,radius:float):
        self.radius = radius

    def calculate_area(self):
        return pi*self.radius*self.radius

class AbsX(metaclass=ABCMeta):
    @abstractmethod
    def helloinst(self):
        raise NotImplementedError

class X(AbsX):
    WORLD="world"

    def hello():
        return "hello " + X.WORLD

    @staticmethod
    def hellostatic():
        return "hello static " + X.WORLD

    def helloinst(self):
        return "Hello inst " + X.WORLD

if __name__=='__main__':
    print( X.hello() )
    print( X.hellostatic() )
    print( X().helloinst() )

    objs = []
    objs.append(Square(2))
    objs.append(Circle(3))

    for o in objs:
        #if isinstance(o,Shape):
        #    print(o.calculate_area())
        assert( isinstance(o,Shape) )
        print(o.calculate_area())
}}}