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1 .. _tut-intro: |
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2 |
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3 ********************** |
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4 Whetting Your Appetite |
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5 ********************** |
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6 |
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7 If you do much work on computers, eventually you find that there's some task |
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8 you'd like to automate. For example, you may wish to perform a |
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9 search-and-replace over a large number of text files, or rename and rearrange a |
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10 bunch of photo files in a complicated way. Perhaps you'd like to write a small |
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11 custom database, or a specialized GUI application, or a simple game. |
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12 |
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13 If you're a professional software developer, you may have to work with several |
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14 C/C++/Java libraries but find the usual write/compile/test/re-compile cycle is |
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15 too slow. Perhaps you're writing a test suite for such a library and find |
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16 writing the testing code a tedious task. Or maybe you've written a program that |
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17 could use an extension language, and you don't want to design and implement a |
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18 whole new language for your application. |
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19 |
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20 Python is just the language for you. |
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21 |
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22 You could write a Unix shell script or Windows batch files for some of these |
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23 tasks, but shell scripts are best at moving around files and changing text data, |
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24 not well-suited for GUI applications or games. You could write a C/C++/Java |
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25 program, but it can take a lot of development time to get even a first-draft |
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26 program. Python is simpler to use, available on Windows, Mac OS X, and Unix |
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27 operating systems, and will help you get the job done more quickly. |
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28 |
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29 Python is simple to use, but it is a real programming language, offering much |
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30 more structure and support for large programs than shell scripts or batch files |
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31 can offer. On the other hand, Python also offers much more error checking than |
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32 C, and, being a *very-high-level language*, it has high-level data types built |
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33 in, such as flexible arrays and dictionaries. Because of its more general data |
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34 types Python is applicable to a much larger problem domain than Awk or even |
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35 Perl, yet many things are at least as easy in Python as in those languages. |
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36 |
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37 Python allows you to split your program into modules that can be reused in other |
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38 Python programs. It comes with a large collection of standard modules that you |
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39 can use as the basis of your programs --- or as examples to start learning to |
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40 program in Python. Some of these modules provide things like file I/O, system |
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41 calls, sockets, and even interfaces to graphical user interface toolkits like |
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42 Tk. |
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43 |
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44 Python is an interpreted language, which can save you considerable time during |
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45 program development because no compilation and linking is necessary. The |
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46 interpreter can be used interactively, which makes it easy to experiment with |
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47 features of the language, to write throw-away programs, or to test functions |
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48 during bottom-up program development. It is also a handy desk calculator. |
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49 |
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50 Python enables programs to be written compactly and readably. Programs written |
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51 in Python are typically much shorter than equivalent C, C++, or Java programs, |
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52 for several reasons: |
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53 |
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54 * the high-level data types allow you to express complex operations in a single |
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55 statement; |
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56 |
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57 * statement grouping is done by indentation instead of beginning and ending |
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58 brackets; |
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59 |
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60 * no variable or argument declarations are necessary. |
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61 |
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62 Python is *extensible*: if you know how to program in C it is easy to add a new |
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63 built-in function or module to the interpreter, either to perform critical |
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64 operations at maximum speed, or to link Python programs to libraries that may |
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65 only be available in binary form (such as a vendor-specific graphics library). |
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66 Once you are really hooked, you can link the Python interpreter into an |
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67 application written in C and use it as an extension or command language for that |
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68 application. |
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69 |
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70 By the way, the language is named after the BBC show "Monty Python's Flying |
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71 Circus" and has nothing to do with reptiles. Making references to Monty |
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72 Python skits in documentation is not only allowed, it is encouraged! |
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73 |
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74 Now that you are all excited about Python, you'll want to examine it in some |
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75 more detail. Since the best way to learn a language is to use it, the tutorial |
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76 invites you to play with the Python interpreter as you read. |
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77 |
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78 In the next chapter, the mechanics of using the interpreter are explained. This |
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79 is rather mundane information, but essential for trying out the examples shown |
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80 later. |
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81 |
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82 The rest of the tutorial introduces various features of the Python language and |
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83 system through examples, beginning with simple expressions, statements and data |
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84 types, through functions and modules, and finally touching upon advanced |
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85 concepts like exceptions and user-defined classes. |
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86 |
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87 |