About this course
Python is an easy to learn, powerful programming language. It has efficient high-level data structures and
a simple but effective approach to object-oriented programming. Python’s elegant syntax and dynamic
typing, together with its interpreted nature, make it an ideal language for scripting and rapid application
development in many areas on most platforms.
The Python interpreter and the extensive standard library are freely available in source or binary form for all
major platforms from the Python Web site, https://www.python.org/, and may be freely distributed. The
same site also contains distributions of and pointers to many free third party Python modules, programs
and tools, and additional documentation.
The Python interpreter is easily extended with new functions and data types implemented in C or C++
(or other languages callable from C). Python is also suitable as an extension language for customizable
applications.
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 all examples are
self-contained, so the tutorial can be read off-line as well.
For a description of standard objects and modules, see library-index. reference-index gives a more formal
definition of the language. To write extensions in C or C++, read extending-index and c-api-index. There
are also several books covering Python in depth.
This tutorial does not attempt to be comprehensive and cover every single feature, or even every commonly
used feature. Instead, it introduces many of Python’s most noteworthy features, and will give you a good
idea of the language’s flavor and style. After reading it, you will be able to read and write Python modules
and programs, and you will be ready to learn more about the various Python library modules described in
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Chapter 1
WHETTING YOUR APPETITE
If you do much work on computers, eventually you find that there’s some task you’d like to automate. For
example, you may wish to perform a search-and-replace over a large number of text files, or rename and
rearrange a bunch of photo files in a complicated way. Perhaps you’d like to write a small custom database,
or a specialized GUI application, or a simple game.
If you’re a professional software developer, you may have to work with several C/C++/Java libraries but
find the usual write/compile/test/re-compile cycle is too slow. Perhaps you’re writing a test suite for such
a library and find writing the testing code a tedious task. Or maybe you’ve written a program that could
use an extension language, and you don’t want to design and implement a whole new language for your
application.
Python is just the language for you
2.1.1 Argument Passing
When known to the interpreter, the script name and additional arguments thereafter are turned into a list
of strings and assigned to the argv variable in the sys module. You can access this list by executing import
sys. The length of the list is at least one; when no script and no arguments are given, sys.argv[0] is an
empty string. When the script name is given as '-' (meaning standard input), sys.argv[0] is set to '-'.
When -c command is used, sys.argv[0] is set to '-c'. When -m module is used, sys.argv[0] is set to
the full name of the located module. Options found after -c command or -m module are not consumed by
the Python interpreter’s option processing but left in sys.argv for the command or module to handle.
Chapter 2
