Python3.0入门指南：A Byte of Python

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"A Byte of Python的3.0版本是一本非常适合初学者的Python编程入门教程，作者用通俗易懂的语言介绍了Python 3.0的基本概念和语法。这本书旨在引导完全不懂计算机基础知识的人学习编程，即使你只知道如何保存文本文件，也能通过这本书开始编程之旅。" 在Python 3.0入门教程中，读者会了解到以下关键知识点： 1. Python 3.0介绍：Python 3.0是Python语言的一个重大更新，它引入了许多新特性，包括改进的语法、内置类型的变化以及对Unicode的更好支持。学习Python 3.0有助于适应现代编程需求。 2. 安装Python：首先，你需要下载并安装Python 3.0解释器，教程会指导你如何在不同的操作系统（如Windows、Mac OS X或Linux）上进行安装。 3. 基础语法：教程将涵盖Python的基础语法，包括变量、数据类型（如整型、浮点型、字符串、列表、元组、字典和集合）、控制流（如条件语句和循环）、函数定义和调用，以及异常处理。 4. 字符串操作：Python 3.0中的字符串是不可变的，且全面支持Unicode。你会学习到字符串的创建、连接、切片、查找、替换和格式化等操作。 5. 模块和包：Python的标准库包含许多预装模块，教程会教你如何导入和使用这些模块，以及如何创建自己的模块和包来组织代码。 6. 面向对象编程：Python是一种面向对象的语言，你将学习类的定义、对象的创建、继承、封装和多态等概念。 7. 文件操作：了解如何打开、读取、写入和关闭文件，这对于数据处理和存储是必不可少的。 8. 标准输入/输出：学习如何从键盘接收输入和向屏幕输出，这是编写交互式程序的基础。 9. 函数式编程：Python支持函数式编程风格，包括高阶函数、闭包和装饰器等概念，这些可以帮助你写出简洁而强大的代码。 10. 错误和调试：学习如何理解和处理运行时错误，以及使用调试工具来找出和修复代码中的问题。此外，"A Byte of Python"还包含了一些实际项目示例，帮助读者将所学知识应用于实践。书中的反馈表明，读者普遍认为这本书对于初学者非常友好，易于理解，是学习Python 3.0的理想起点。如果你正在寻找Python编程的启蒙书籍，这本书无疑是一个很好的选择。

Python en:Introduction

Features of Python

Simple

Python is a simple and minimalistic language. Reading a good Python program feels

almost like reading English, although very strict English! This pseudo-code nature of

Python is one of its greatest strengths. It allows you to concentrate on the solution to

the problem rather than the language itself.

Easy to Learn

As you will see, Python is extremely easy to get started with. Python has an

extraordinarily simple syntax, as already mentioned.

Free and Open Source

Python is an example of a FLOSS (Free/Libré and Open Source Software). In simple

terms, you can freely distribute copies of this software, read its source code, make

changes to it, and use pieces of it in new free programs. FLOSS is based on the

concept of a community which shares knowledge. This is one of the reasons why

Python is so good - it has been created and is constantly improved by a community who

just want to see a better Python.

High-level Language

When you write programs in Python, you never need to bother about the low-level

details such as managing the memory used by your program, etc.

Portable

Due to its open-source nature, Python has been ported to (i.e. changed to make it work

on) many platforms. All your Python programs can work on any of these platforms

without requiring any changes at all if you are careful enough to avoid any

system-dependent features.

You can use Python on Linux, Windows, FreeBSD, Macintosh, Solaris, OS/2, Amiga,

AROS, AS/400, BeOS, OS/390, z/OS, Palm OS, QNX, VMS, Psion, Acorn RISC OS,

VxWorks, PlayStation, Sharp Zaurus, Windows CE and even PocketPC !

Interpreted

This requires a bit of explanation.

A program written in a compiled language like C or C++ is converted from the source

language i.e. C or C++ into a language that is spoken by your computer (binary code

i.e. 0s and 1s) using a compiler with various flags and options. When you run the

program, the linker/loader software copies the program from hard disk to memory and

starts running it.

Python, on the other hand, does not need compilation to binary. You just run the

program directly from the source code. Internally, Python converts the source code

into an intermediate form called bytecodes and then translates this into the native

language of your computer and then runs it. All this, actually, makes using Python

much easier since you don't have to worry about compiling the program, making sure

that the proper libraries are linked and loaded, etc, etc. This also makes your Python

programs much more portable, since you can just copy your Python program onto

another computer and it just works!

Object Oriented

Python en:Introduction

Python supports procedure-oriented programming as well as object-oriented

programming. In procedure-oriented languages, the program is built around

procedures or functions which are nothing but reusable pieces of programs. In

object-oriented languages, the program is built around objects which combine data

and functionality. Python has a very powerful but simplistic way of doing OOP,

especially when compared to big languages like C++ or Java.

Extensible

If you need a critical piece of code to run very fast or want to have some piece of

algorithm not to be open, you can code that part of your program in C or C++ and

then use it from your Python program.

Embeddable

You can embed Python within your C/C++ programs to give 'scripting' capabilities for

your program's users.

Extensive Libraries

The Python Standard Library is huge indeed. It can help you do various things

involving regular expressions, documentation generation, unit testing, threading,

databases, web browsers, CGI, FTP, email, XML, XML-RPC, HTML, WAV files,

cryptography, GUI (graphical user interfaces), Tk, and other system-dependent stuff.

Remember, all this is always available wherever Python is installed. This is called the

'Batteries Included' philosophy of Python.

Besides, the standard library, there are various other high-quality libraries such as

wxPython

[1]

, Twisted

[2]

, Python Imaging Library

[3]

and many more.

Python is indeed an exciting and powerful language. It has the right combination of

performance and features that make writing programs in Python both fun and easy.

Why not Perl?

If you didn't know already, Perl is another extremely popular open source interpreted

programming language.

If you have ever tried writing a large program in Perl, you would have answered this

question yourself! In other words, Perl programs are easy when they are small and it excels

at small hacks and scripts to 'get work done'. However, they quickly become unwieldy once

you start writing bigger programs and I am speaking this out of my experience writing

large Perl programs at Yahoo!

When compared to Perl, Python programs are definitely simpler, clearer, easier to write

and hence more understandable and maintainable. I do admire Perl and I do use it on a

daily basis for various things but whenever I write a program, I always start thinking in

terms of Python because it has become so natural for me. Perl has undergone so many

hacks and changes, that it feels like it is one big (but one hell of a) hack. Sadly, the

upcoming Perl 6 does not seem to be making any improvements regarding this.

The only and very significant advantage that I feel Perl has, is its huge CPAN

[4]

library - the

Comprehensive Perl Archive Network. As the name suggests, this is a humongous collection

of Perl modules and it is simply mind-boggling because of its sheer size and depth - you can

do virtually anything you can do with a computer using these modules. One of the reasons

that Perl has more libraries than Python is that it has been around for a much longer time

than Python. However this seems to be changing with the growing Python Package Index

Python en:Introduction

[5]

Why not Ruby?

If you didn't know already, Ruby is another popular open source interpreted programming

language.

If you already like and use Ruby, then I would definitely recommend you to continue using

it.

For other people who have not used it and are trying to judge whether to learn Python or to

learn Ruby, then I would recommend Python, purely from an ease-of-learning perspective. I

personally found it hard to grok the Ruby language, but for people who understand Ruby,

they all praise the beauty of the language. Unfortunately, I am not as lucky.

What Programmers Say

You may find it interesting to read what great hackers like ESR have to say about Python:

• Eric S. Raymond is the author of "The Cathedral and the Bazaar" and is also the person

who coined the term Open Source. He says that Python has become his favorite

programming language

[6]

. This article was the real inspiration for my first brush with

Python.

• Bruce Eckel is the author of the famous Thinking in Java and Thinking in C++ books. He

says that no language has made him more productive than Python. He says that Python is

perhaps the only language that focuses on making things easier for the programmer.

Read the complete interview

[7]

for more details.

• Peter Norvig is a well-known Lisp author and Director of Search Quality at Google

(thanks to Guido van Rossum for pointing that out). He says that Python has always been

an integral part of Google. You can actually verify this statement by looking at the Google

Jobs

[8]

page which lists Python knowledge as a requirement for software engineers.

About Python 3. 0

Python 3.0 is the upcoming new version of the language. It is sometimes referred to as

Python 3000 or Py3K.

The main reason for a major new version of Python is to remove all the small problems and

nitpicks that have accumulated over the years and to make the language even more clean.

If you already have a lot of Python 2.x code, then there is a utility to assist you to convert

2.x to 3.x source

[9]

More details are at:

• Guido van Rossum's introduction

[10]

• What's New in Python 2.6

[11]

(features significantly different from previous Python 2.x

versions and most likely will be included in Python 3.0)

• What's New in Python 3.0

[12]

• Python 2.6 and 3.0 Release Schedule

[13]

• Python 3000 (the official authoritative list of proposed changes)

[14]

• Miscellaneous Python 3.0 Plans

[15]

• Python News (detailed list of changes)

[16]

Python en:Installation

However, if you get a message like this one:

$ python -V

bash: Python: command not found

Then you don't have Python installed. This is highly unlikely but possible.

In this case, you have two ways of installing Python on your system.

• You can compile Python from the source code

[1]

and install it. The compilation

instructions are provided at the website.

• [This option will be available after the final release of Python 3.0] Install the binary

packages using the package management software that comes with your OS, such as

apt-get in Ubuntu/Debian and other Debian-based Linux, yum in Fedora Linux, pkg_add

in FreeBSD, etc. Note that you will need an internet connection to use this method.

Alternatively, you can download the binaries from somewhere else and then copy to your

PC and install it.

For Windows Users

Visit http:/ / www. python. org/ download/ releases/ 3. 0/ and download the latest version

from this website, which was 3.0 beta 1

[2]

as of this writing. This is just 12.8 MB which is

very compact compared to most other languages or software. The installation is just like

any other Windows-based software.

Caution

When you are given the option of unchecking any "optional" components, don't

uncheck any! Some of these components can be useful for you, especially IDLE.

An interesting fact is that majority of Python downloads are by Windows users. Of course,

this doesn't give the complete picture since almost all Linux users will have Python installed

already on their systems by default.

DOS Prompt

If you want to be able to use Python from the Windows command line i.e. the DOS prompt,

then you need to set the PATH variable appropriately.

For Windows 2000, XP, 2003 , click on Control Panel -> System -> Advanced ->

Environment Variables. Click on the variable named PATH in the 'System Variables'

section, then select Edit and add ;C:\Python30 to the end of what is already there. Of

course, use the appropriate directory name.

For older versions of Windows, add the following line to the file C:\AUTOEXEC.BAT :

'PATH=%PATH%;C:\Python30' (without the quotes) and restart the system. For Windows NT,

use the AUTOEXEC.NT file.

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