Python Tutorial ( PDFDrive )

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Python Environment Variables: Here are important environment variables, which can be recognized by Python:VariablePYTHONPATHPYTHONSTARTUPPYTHONCASEOKDescriptionHas a role similar to PATH. This variable tells the Python interpreter where to locate themodule files you import into a program. PYTHONPATH should include the Python sourcelibrary directory and the directories containing your Python source code. PYTHONPATH issometimes preset by the Python installer.Contains the path of an initialization file containing Python source code that is executedevery time you start the interpreter (similar to the Unix .profile or .login file). This file, oftennamed .pythonrc.py in Unix, usually contains commands that load utilities or modifyPYTHONPATH.Used in Windows to instruct Python to find the first case-insensitive match in an importstatement. Set this variable to any value to activate it.PYTHONHOMERunning Python: An alternative module search path. It's usually embedded in the PYTHONSTARTUP orPYTHONPATH directories to make switching module libraries easy.There are three different ways to start Python:(1) Interactive Interpreter: You can enter python and start coding right away in the interactive interpreter by starting it from the commandline. You can do this from Unix, DOS or any other system, which provides you a command-line interpreter or shellwindow.$python# Unix/Linuxorpython%# Unix/LinuxorC:>python# Windows/DOSHere is the list of all the available command line options:OptionDescription-d provide debug output-O generate optimized bytecode (resulting in .pyo files)-S do not run import site to look for Python paths on startup-v verbose output (detailed trace on import statements)-X disable class-based built-in exceptions (just use strings); obsolete starting with version 1.6TUTORIALS POINT Simply Easy Learning
-c cmd run Python script sent in as cmd stringfilerun Python script from given file(2) Script from the Command-‐line: A Python script can be executed at command line by invoking the interpreter on your application, as in thefollowing:$python script.py# Unix/Linuxorpython% script.py# Unix/LinuxorC:>python script.py# Windows/DOSNote: Be sure the file permission mode allows execution.(3) Integrated Development Environment You can run Python from a graphical user interface (GUI) environment as well. All you need is a GUI applicationon your system that supports Python.• Unix: IDLE is the very first Unix IDE for Python.• Windows: PythonWin is the first Windows interface for Python and is an IDE with a GUI.• Macintosh: The Macintosh version of Python along with the IDLE IDE is available from the main website,downloadable as either MacBinary or BinHex'd files.Before proceeding to next chapter, make sure your environment is properly set up and working perfectly fine. Ifyou are not able to set up the environment properly, then you can take help from your system admin.All the examples given in subsequent chapters have been executed with Python 2.4.3 version available onCentOS flavor of Linux.TUTORIALS POINT Simply Easy Learning
Page 1 and 2: Python Tutorial
Page 3 and 4: ABOUT THE TUTORIALPython TutorialPy
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Page 41 and 42: CHAPTER1Python OverviewPython is a
Page 43 and 44: CHAPTER2Python EnvironmentBefore we
Page 45: • To use this installer python-XY
Page 49 and 50: This will produce the following res
Page 51 and 52: file_name = raw_input("Enter filena
Page 53 and 54: $ python -husage: python [option] .
Page 55 and 56: print 'Input file is "', inputfilep
Page 57 and 58: Here, an integer object is created
Page 59 and 60: Python Lists: Lists are the most v
Page 61 and 62: FunctionDescriptionint(x [,base])Co
Page 63 and 64: CHAPTER5Python Basic OperatorsWhat
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Page 67 and 68: Line 5 - a is greater than bLine 6
Page 69 and 70: | Binary OR Operator copies a bit i
Page 71 and 72: else:print "Line 3 - a and b are tr
Page 73 and 74: if ( id(a) == id(b) ):print "Line 2
Page 75 and 76: When you execute the above program,
Page 77 and 78: if statementsif...else statementsne
Page 79 and 80: Example: #!/usr/bin/pythonvar1 = 10
Page 81 and 82: else:print "Could not find true exp
Page 83 and 84: Loop Typewhile loopfor loopDescript
Page 85 and 86: num = raw_input("Enter a number :")
Page 87 and 88: Good bye!Iterating by Sequence I
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Syntax Following is the syntax for
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import math# This will import math
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import mathmath.log10( x )Note: Thi
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modf(x) Description The method modf
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round( x [, n] )Parameters • x --
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Return Value This method returns a
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seed([x]) Description The method se
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asin(x)Note: This function is not a
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print "atan2(-10,10) : ", math.atan
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Note: This function is not accessib
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import mathprint "degrees(3) : ", m
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CHAPTER9Python StringsStrings are a
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+ Concatenation - Adds values on ei
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TAB ( \t ) and they will show up th
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str = "this is string example....wo
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Return Value This method returns a
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Description The method expandtabs()
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Traceback (most recent call last):F
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Let us compile and run the above pr
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str = "This is string example....wo
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str = "-";seq = ("a", "b", "c"); #
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lstrip() Description The method lst
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Max character: xmin(str) Descriptio
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str = "this is really a string exam
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Parameters • chars -- You can sup
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Parameters• str -- This is the st
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Parameters • NAReturn Value This
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Example The following example shows
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CHAPTER10Python ListsThe most basic
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Python Expression Results Descripti
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list( seq )Parameters • seq -- Th
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Return Value If elements are of th
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list.insert(index, obj)Parameters
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CHAPTER11Python TuplesAtuple is a s
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len((1, 2, 3)) 3 Length(1, 2, 3) +
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-11-1len(tuple) Description The met
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min value element : 200tuple(seq) D
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#!/usr/bin/pythondict = {'Name': 'Z
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34str(dict)Produces a printable str
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type(variable) Description The meth
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Return Value This method does not
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CHAPTER13Python Date & TimeApython
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#!/usr/bin/pythonimport time;localt
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import timeprint "time.altzone %d "
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Parameters • sec -- These are the
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• %w - day of the week as a decim
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time.time( ) Description The metho
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2time.tznameAttribute time.tzname i
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CHAPTER14Python FunctionAfunction i
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#!/usr/bin/python# Function definit
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return;# Now you can call printinfo
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Inside the function : 30Outside the
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A module is loaded only once, regar
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'sqrt', 'tan', 'tanh']Here, the spe
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CHAPTER16Python Files I/OThis chapt
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rb+WWbw+wb+AAba+ab+Opens a file for
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fo.write( "Python is a great langua
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EXAMPLE: Following is the example t
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operations from the operating syste
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# Close opened filefo.close()Let us
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Parameters • NAReturn Value This
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Parameters • offset -- This is th
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Parameters • size -- If this opti
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Description The method writelines()
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53545556575859606162os.symlink(src,
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• stat.S_IRGRP: Read by group.•
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os.chroot("/tmp/usr")print "Changed
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Parameters • fd -- This is the or
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import os, sys# First go to the "/v
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Description The method fchown() cha
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Description The method fdopen() ret
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{'PC_MAX_INPUT': 2, 'PC_VDISABLE':
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# Open a filefd = os.open( "foo.txt
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print "Current working dir : %s" %
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path = "/var/www/html/foo.txt"fd =
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_vti_txtrobots.txtitemlistingresume
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# Close opened fileos.close( fd )#
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dev_num = os.makedev(major_dnum, mi
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-rw-------. 1 root root 0 Apr 30 02
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os.pathconf(path, name) Descriptio
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Description The method popen() open
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# !/usr/bin/pythonimport ossrc = '/
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# stat informationstatinfo = os.sta
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Description The method tcgetpgrp()
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os.tempnam(dir, prefix)Parameters
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Description The method ttyname() re
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Return Value This method returns t
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KeyErrorNameErrorUnboundLocalErrorE
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......................else:If there
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print "Error: can\'t find file or r
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self.args = argSo once you defined
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'Optional class documentation strin
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For the above class let's try to ac
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print 'Calling child method'c = Chi
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Data Hiding: An object's attribute
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groups()This method returns all mat
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SYNTAX: re.sub(pattern, repl, strin
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\s Matches whitespace. Equivalent t
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Backreferences: This matches a prev
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CHAPTER20Python CGI ProgrammingWhat
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If you click hello.py, then this pr
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Simple URL Example : Get Metho
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</form>The result of this code is t
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text_content = form.getvalue('textc
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Here is an example of how to retrie
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CHAPTER21Python Database AccessThe
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EXAMPLE: Following is the example o
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('Mac', 'Mohan', 20, 'M', 2000)try:
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DELETE Operation: DELETE operation
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ProgrammingErrorSubclass of Databas
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The socket Module: To create a so
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Protocol Common function Port No Py
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Subject: SMTP e-mail testThis is a
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try:smtpObj = smtplib.SMTP('localho
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count = 0while count < 5:time.sleep
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Synchronizing Threads: The threadi
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thread = myThread(threadID, tName,
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<stars>10</stars><description>Talk
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print "Rating:", self.ratingelif se
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Format: DVDRating: PGDescription: T
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Tkinter Widgets Tkinter provides v
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fgfontheighthighlightcolorimagejust
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WidthXscrollincrementXscrollcommand
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pattern when it is over the checkbu
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The Entry widget is used to accept
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E1 = Entry(top, bd =5)E1.pack(side
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Optionanchorbgbitmapbdcursorfontfgh
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selectmodeDetermines how many items
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Syntax: Here is the simple syntax t
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Menu The goal of this widget is to
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filemenu.add_command(label="Exit",
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Example: Try the following example
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WidthWraplengthWidth of the label i
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label appears in the top left corne
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Parameters: • master: This repres
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Parameters: • master: This repres
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mark_gravity(mark [,gravity])Return
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Methods & Descriptiondeiconify()Dis
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disabledbackgrounddisabledforegroun
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bgbdThe color of the slider and arr
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fontheightlabelAnchorhighlightbackg
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Standard attributes:Let's take a l
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• family: The font family name as
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B2.pack()B3.pack()B4.pack()B5.pack(
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• "heart"• "heart"• "man"•
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The grid() Method This geometry m
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CHAPTERPython Further Extensions27A
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This table needs to be terminated w
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Passing Function Parameters: Beca
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return (a + b)You can return two va
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CHAPTER28Python Tools/UtilitiesThe
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The profile Module: The profile m
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