mirror of https://github.com/python/cpython
88 lines
4.4 KiB
ReStructuredText
88 lines
4.4 KiB
ReStructuredText
.. _tut-intro:
|
|
|
|
**********************
|
|
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.
|
|
|
|
You could write a Unix shell script or Windows batch files for some of these
|
|
tasks, but shell scripts are best at moving around files and changing text data,
|
|
not well-suited for GUI applications or games. You could write a C/C++/Java
|
|
program, but it can take a lot of development time to get even a first-draft
|
|
program. Python is simpler to use, available on Windows, MacOS X, and Unix
|
|
operating systems, and will help you get the job done more quickly.
|
|
|
|
Python is simple to use, but it is a real programming language, offering much
|
|
more structure and support for large programs than shell scripts or batch files
|
|
can offer. On the other hand, Python also offers much more error checking than
|
|
C, and, being a *very-high-level language*, it has high-level data types built
|
|
in, such as flexible arrays and dictionaries. Because of its more general data
|
|
types Python is applicable to a much larger problem domain than Awk or even
|
|
Perl, yet many things are at least as easy in Python as in those languages.
|
|
|
|
Python allows you to split your program into modules that can be reused in other
|
|
Python programs. It comes with a large collection of standard modules that you
|
|
can use as the basis of your programs --- or as examples to start learning to
|
|
program in Python. Some of these modules provide things like file I/O, system
|
|
calls, sockets, and even interfaces to graphical user interface toolkits like
|
|
Tk.
|
|
|
|
Python is an interpreted language, which can save you considerable time during
|
|
program development because no compilation and linking is necessary. The
|
|
interpreter can be used interactively, which makes it easy to experiment with
|
|
features of the language, to write throw-away programs, or to test functions
|
|
during bottom-up program development. It is also a handy desk calculator.
|
|
|
|
Python enables programs to be written compactly and readably. Programs written
|
|
in Python are typically much shorter than equivalent C, C++, or Java programs,
|
|
for several reasons:
|
|
|
|
* the high-level data types allow you to express complex operations in a single
|
|
statement;
|
|
|
|
* statement grouping is done by indentation instead of beginning and ending
|
|
brackets;
|
|
|
|
* no variable or argument declarations are necessary.
|
|
|
|
Python is *extensible*: if you know how to program in C it is easy to add a new
|
|
built-in function or module to the interpreter, either to perform critical
|
|
operations at maximum speed, or to link Python programs to libraries that may
|
|
only be available in binary form (such as a vendor-specific graphics library).
|
|
Once you are really hooked, you can link the Python interpreter into an
|
|
application written in C and use it as an extension or command language for that
|
|
application.
|
|
|
|
By the way, the language is named after the BBC show "Monty Python's Flying
|
|
Circus" and has nothing to do with nasty reptiles. Making references to Monty
|
|
Python skits in documentation is not only allowed, it is encouraged!
|
|
|
|
Now that you are all excited about Python, you'll want to examine it in some
|
|
more detail. Since the best way to learn a language is to use it, the tutorial
|
|
invites you to play with the Python interpreter as you read.
|
|
|
|
In the next chapter, the mechanics of using the interpreter are explained. This
|
|
is rather mundane information, but essential for trying out the examples shown
|
|
later.
|
|
|
|
The rest of the tutorial introduces various features of the Python language and
|
|
system through examples, beginning with simple expressions, statements and data
|
|
types, through functions and modules, and finally touching upon advanced
|
|
concepts like exceptions and user-defined classes.
|
|
|
|
|