author | William Roberts <williamr@symbian.org> |
Thu, 08 Oct 2009 20:49:04 +0100 | |
changeset 10 | 1cf69c2c2bbd |
parent 1 | 2fb8b9db1c86 |
permissions | -rw-r--r-- |
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.. _tut-intro: |
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********************** |
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Whetting Your Appetite |
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********************** |
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If you do much work on computers, eventually you find that there's some task |
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you'd like to automate. For example, you may wish to perform a |
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search-and-replace over a large number of text files, or rename and rearrange a |
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bunch of photo files in a complicated way. Perhaps you'd like to write a small |
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custom database, or a specialized GUI application, or a simple game. |
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If you're a professional software developer, you may have to work with several |
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C/C++/Java libraries but find the usual write/compile/test/re-compile cycle is |
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too slow. Perhaps you're writing a test suite for such a library and find |
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writing the testing code a tedious task. Or maybe you've written a program that |
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could use an extension language, and you don't want to design and implement a |
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whole new language for your application. |
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Python is just the language for you. |
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You could write a Unix shell script or Windows batch files for some of these |
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tasks, but shell scripts are best at moving around files and changing text data, |
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not well-suited for GUI applications or games. You could write a C/C++/Java |
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program, but it can take a lot of development time to get even a first-draft |
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program. Python is simpler to use, available on Windows, Mac OS X, and Unix |
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operating systems, and will help you get the job done more quickly. |
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Python is simple to use, but it is a real programming language, offering much |
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more structure and support for large programs than shell scripts or batch files |
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can offer. On the other hand, Python also offers much more error checking than |
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C, and, being a *very-high-level language*, it has high-level data types built |
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in, such as flexible arrays and dictionaries. Because of its more general data |
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types Python is applicable to a much larger problem domain than Awk or even |
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Perl, yet many things are at least as easy in Python as in those languages. |
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Python allows you to split your program into modules that can be reused in other |
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Python programs. It comes with a large collection of standard modules that you |
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can use as the basis of your programs --- or as examples to start learning to |
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program in Python. Some of these modules provide things like file I/O, system |
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calls, sockets, and even interfaces to graphical user interface toolkits like |
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Tk. |
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Python is an interpreted language, which can save you considerable time during |
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program development because no compilation and linking is necessary. The |
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interpreter can be used interactively, which makes it easy to experiment with |
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features of the language, to write throw-away programs, or to test functions |
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during bottom-up program development. It is also a handy desk calculator. |
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Python enables programs to be written compactly and readably. Programs written |
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in Python are typically much shorter than equivalent C, C++, or Java programs, |
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for several reasons: |
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* the high-level data types allow you to express complex operations in a single |
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statement; |
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* statement grouping is done by indentation instead of beginning and ending |
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brackets; |
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* no variable or argument declarations are necessary. |
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Python is *extensible*: if you know how to program in C it is easy to add a new |
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built-in function or module to the interpreter, either to perform critical |
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operations at maximum speed, or to link Python programs to libraries that may |
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only be available in binary form (such as a vendor-specific graphics library). |
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Once you are really hooked, you can link the Python interpreter into an |
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application written in C and use it as an extension or command language for that |
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application. |
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By the way, the language is named after the BBC show "Monty Python's Flying |
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Circus" and has nothing to do with reptiles. Making references to Monty |
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Python skits in documentation is not only allowed, it is encouraged! |
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Now that you are all excited about Python, you'll want to examine it in some |
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more detail. Since the best way to learn a language is to use it, the tutorial |
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invites you to play with the Python interpreter as you read. |
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In the next chapter, the mechanics of using the interpreter are explained. This |
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is rather mundane information, but essential for trying out the examples shown |
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later. |
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The rest of the tutorial introduces various features of the Python language and |
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system through examples, beginning with simple expressions, statements and data |
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types, through functions and modules, and finally touching upon advanced |
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concepts like exceptions and user-defined classes. |
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