Python Tutorial ( PDFDrive )

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COMMIT Operation: Commit is the operation, which gives a green signal to database to finalize the changes, and after this operation,no change can be reverted back.Here is a simple example to call commit method.db.commit()ROLLBACK Operation: If you are not satisfied with one or more of the changes and you want to revert back those changes completely,then use rollback() method.Here is a simple example to call rollback() method.db.rollback()Disconnecting Database: To disconnect Database connection, use close() method.db.close()If the connection to a database is closed by the user with the close() method, any outstanding transactions arerolled back by the DB. However, instead of depending on any of DB lower level implementation details, yourapplication would be better off calling commit or rollback explicitly.Handling Errors: There are many sources of errors. A few examples are a syntax error in an executed SQL statement, aconnection failure, or calling the fetch method for an already canceled or finished statement handle.The DB API defines a number of errors that must exist in each database module. The following table lists theseexceptions.ExceptionWarningErrorInterfaceErrorDatabaseErrorDataErrorOperationalErrorIntegrityErrorInternalErrorDescriptionUsed for non-fatal issues. Must subclass StandardError.Base class for errors. Must subclass StandardError.Used for errors in the database module, not the database itself. Must subclassError.Used for errors in the database. Must subclass Error.Subclass of DatabaseError that refers to errors in the data.Subclass of DatabaseError that refers to errors such as the loss of a connection tothe database. These errors are generally outside of the control of the Pythonscripter.Subclass of DatabaseError for situations that would damage the relational integrity,such as uniqueness constraints or foreign keys.Subclass of DatabaseError that refers to errors internal to the database module,such as a cursor no longer being active.TUTORIALS POINT Simply Easy Learning
ProgrammingErrorSubclass of DatabaseError that refers to errors such as a bad table name andother things that can safely be blamed on you.NotSupportedError Subclass of DatabaseError that refers to trying to call unsupported functionality.Your Python scripts should handle these errors, but before using any of the above exceptions, make sure yourMySQLdb has support for that exception. You can get more information about them by reading the DB API 2.0specification.TUTORIALS POINT Simply Easy Learning
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Python Tutorial
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ABOUT THE TUTORIALPython TutorialPy
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Description .......................
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Parameters ........................
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Locating Modules: .................
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Description .......................
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Return Value ......................
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Example ...........................
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Parameters ........................
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Regular-expression Modifiers - Opti
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Starting a New Thread: ............
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Example: ..........................
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CHAPTER1Python OverviewPython is a
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CHAPTER2Python EnvironmentBefore we
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• To use this installer python-XY
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-c cmd run Python script sent in as
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This will produce the following res
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file_name = raw_input("Enter filena
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$ python -husage: python [option] .
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print 'Input file is "', inputfilep
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Here, an integer object is created
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Python Lists: Lists are the most v
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FunctionDescriptionint(x [,base])Co
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CHAPTER5Python Basic OperatorsWhat
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Line 4 - Value of c is 2Line 5 - Va
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Line 5 - a is greater than bLine 6
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| Binary OR Operator copies a bit i
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else:print "Line 3 - a and b are tr
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if ( id(a) == id(b) ):print "Line 2
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When you execute the above program,
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if statementsif...else statementsne
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Example: #!/usr/bin/pythonvar1 = 10
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else:print "Could not find true exp
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Loop Typewhile loopfor loopDescript
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num = raw_input("Enter a number :")
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Good bye!Iterating by Sequence I
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11 is prime13 is prime17 is prime19
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continue statement The continue st
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CHAPTER8Python NumbersNumber data t
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max(x1, x2,...)min(x1, x2,...)modf(
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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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Page 309 and 310: self.args = argSo once you defined
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Page 315 and 316: print 'Calling child method'c = Chi
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Page 323 and 324: \s Matches whitespace. Equivalent t
Page 325 and 326: Backreferences: This matches a prev
Page 327 and 328: CHAPTER20Python CGI ProgrammingWhat
Page 329 and 330: If you click hello.py, then this pr
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Page 353 and 354: Subject: SMTP e-mail testThis is a
Page 355 and 356: try:smtpObj = smtplib.SMTP('localho
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Page 365 and 366: print "Rating:", self.ratingelif se
Page 367 and 368: Format: DVDRating: PGDescription: T
Page 369 and 370: Tkinter Widgets Tkinter provides v
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Page 377 and 378: The Entry widget is used to accept
Page 379 and 380: E1 = Entry(top, bd =5)E1.pack(side
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Page 383 and 384: selectmodeDetermines how many items
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Page 387 and 388: Menu The goal of this widget is to
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Page 391 and 392: Example: Try the following example
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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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