Python Tutorial

Guido van Rossum
Corporation for National Research Initiatives (CNRI)
1895 Preston White Drive, Reston, Va 20191, USA
E-mail: guido@CNRI.Reston.Va.US, guido@python.org

October 25, 1996
Release 1.4

Copyright © 1991-1995 by Stichting Mathematisch Centrum, Amsterdam, The Netherlands.

All Rights Reserved

Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation, and that the names of Stichting Mathematisch Centrum or CWI or Corporation for National Research Initiatives or CNRI not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission.

While CWI is the initial source for this software, a modified version is made available by the Corporation for National Research Initiatives (CNRI) at the Internet address ftp://ftp.python.org.

STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

Abstract:

Python is a simple, yet powerful programming language that bridges the gap between C and shell programming, and is thus ideally suited for ``throw-away programming'' and rapid prototyping. Its syntax is put together from constructs borrowed from a variety of other languages; most prominent are influences from ABC, C, Modula-3 and Icon.

The Python interpreter is easily extended with new functions and data types implemented in C. Python is also suitable as an extension language for highly customizable C applications such as editors or window managers.

Python is available for various operating systems, amongst which several flavors of Unix, the Apple Macintosh, MS-DOS, Windows (3.1(1), '95 and NT flavors), OS/2, and others.

This tutorial introduces the reader informally to the basic concepts and features of the Python language and system. It helps to have a Python interpreter handy for hands-on experience, but as the examples are self-contained, the tutorial can be read off-line as well.

For a description of standard objects and modules, see the Python Library Reference document. The Python Reference Manual gives a more formal definition of the language.

• Contents
• 1 Whetting Your Appetite
  • 1.1 Disclaimer
  • 1.2 Introduction
  • 1.3 Where From Here
• 2 Using the Python Interpreter
  • 2.1 Invoking the Interpreter
    • 2.1.1 Argument Passing
    • 2.1.2 Interactive Mode
  • 2.2 The Interpreter and its Environment
    • 2.2.1 Error Handling
    • 2.2.2 The Module Search Path
    • 2.2.3 ``Compiled'' Python files
    • 2.2.4 Executable Python scripts
    • 2.2.5 The Interactive Startup File
  • 2.3 Interactive Input Editing and History Substitution
    • 2.3.1 Line Editing
    • 2.3.2 History Substitution
    • 2.3.3 Key Bindings
    • 2.3.4 Commentary
• 3 An Informal Introduction to Python
  • 3.1 Using Python as a Calculator
    • 3.1.1 Numbers
    • 3.1.2 Strings
    • 3.1.3 Lists
  • 3.2 First Steps Towards Programming
• 4 More Control Flow Tools
  • 4.1 If Statements
  • 4.2 For Statements
  • 4.3 The range() Function
  • 4.4 Break and Continue Statements, and Else Clauses on Loops
  • 4.5 Pass Statements
  • 4.6 Defining Functions
• 5 Odds and Ends
  • 5.1 More on Lists
  • 5.2 The del statement
  • 5.3 Tuples and Sequences
  • 5.4 Dictionaries
  • 5.5 More on Conditions
  • 5.6 Comparing Sequences and Other Types
• 6 Modules
  • 6.1 More on Modules
  • 6.2 Standard Modules
  • 6.3 The dir() function
• 7 Output Formatting
• 8 Errors and Exceptions
  • 8.1 Syntax Errors
  • 8.2 Exceptions
  • 8.3 Handling Exceptions
  • 8.4 Raising Exceptions
  • 8.5 User-defined Exceptions
  • 8.6 Defining Clean-up Actions
• 9 Classes
  • 9.1 A word about terminology
  • 9.2 Python scopes and name spaces
  • 9.3 A first look at classes
    • 9.3.1 Class definition syntax
    • 9.3.2 Class objects
    • 9.3.3 Instance objects
    • 9.3.4 Method objects
  • 9.4 Random remarks
  • 9.5 Inheritance
    • 9.5.1 Multiple inheritance
  • 9.6 Odds and ends
• 10 Recent Additions as of Release 1.1
  • 10.1 The Last Printed Expression
  • 10.2 String Literals
    • 10.2.1 Double Quotes
    • 10.2.2 Continuation Of String Literals
    • 10.2.3 Triple-quoted strings
    • 10.2.4 String Literal Juxtaposition
  • 10.3 The Formatting Operator
    • 10.3.1 Basic Usage
    • 10.3.2 Referencing Variables By Name
  • 10.4 Optional Function Arguments
    • 10.4.1 Default Argument Values
    • 10.4.2 Arbitrary Argument Lists
  • 10.5 Lambda And Functional Programming Tools
    • 10.5.1 Lambda Forms
    • 10.5.2 Map, Reduce and Filter
  • 10.6 Continuation Lines Without Backslashes
  • 10.7 Regular Expressions
  • 10.8 Generalized Dictionaries
  • 10.9 Miscellaneous New Built-in Functions
  • 10.10 Else Clause For Try Statement
  • 10.11 New Class Features in Release 1.1
    • 10.11.1 New Operator Overloading
    • 10.11.2 Trapping Attribute Access
    • 10.11.3 Calling a Class Instance
• 11 New in Release 1.2
  • 11.1 New Class Features
  • 11.2 Unix Signal Handling
  • 11.3 Exceptions Can Be Classes
  • 11.4 Object Persistency and Object Copying
    • 11.4.1 Persistent Objects
    • 11.4.2 Copying Objects
  • 11.5 Documentation Strings
  • 11.6 Customizing Import and Built-Ins
  • 11.7 Python and the World-Wide Web
  • 11.8 Miscellaneous
• 12 New in Release 1.3
  • 12.1 Keyword Arguments
  • 12.2 Changes to the WWW and Internet tools
  • 12.3 Other Language Changes
  • 12.4 Changes to Built-in Operations
  • 12.5 Library Changes
  • 12.6 Other Changes
• 13 New in Release 1.4
  • 13.1 Language Changes
  • 13.2 Run-time Changes
  • 13.3 New or Updated Modules
  • 13.4 Configuration and Installation
• About this document ...