TableOfContents

Python语言简介

1. 总览

Python is an interpreted programming language created by Guido van Rossum in 1990. Python is fully dynamically typed and uses automatic memory management; it is thus similar to Perl, Ruby, Scheme, Smalltalk, and Tcl. Python is developed as an open source project, managed by the non-profit Python Software Foundation, and is available for free from the project website. Python 2.4.3 was released on March 29, 2006.

Paradigm编程范式:

Multi-paradigm多范式

Appeared in出现时间:

1990

Designed by设计者:

Guido van Rossum

Developer开发者:

Python Software Foundation

Latest release最后发布时间:

2.4.3 / March 29, 2006

Typing discipline类型规则:

Strong, dynamic ("duck")

Major implementations主要实现:

CPython, Jython, IronPython, PyPy

Influenced by受哪些语言影响:

ABC, Modula-3, Icon, C, Perl, Lisp, Smalltalk, Tcl

Influenced影响了哪些语言:

Ruby, Boo

OS操作系统:

Cross-platform

License许可证:

Python Software Foundation License

Website网站:

www.python.org

2. Python设计哲学

Python is a multi-paradigm language. This means that, rather than forcing coders to adopt one particular style of coding, it permits several. Object orientation, structured programming, functional programming, and aspect-oriented programming are all supported. Other paradigms can be supported through extensions, such as pyDBC and Contracts for Python which allow Design by Contract. Python is dynamically type-checked and uses garbage collection for memory management. An important feature of Python is dynamic name resolution, which binds method and variable names during program execution.

While offering choice in coding methodology, Python's designers reject exuberant syntax, such as in Perl, in favor of a sparser, less cluttered one. As with Perl, Python's developers expressly promote a particular "culture" or ideology based on what they want the language to be, favoring language forms they see as "beautiful", "explicit" and "simple". For the most part, Perl and Python users differ in their interpretation of these terms and how they are best implemented (see TIMTOWTDI and PythonPhilosophy).

Another important goal of the Python developers is making Python fun to use. This is reflected in the origin of the name (after the television series Monty Python's Flying Circus), in the common practice of using Monty Python references in example code, and in an occasionally playful approach to tutorials and reference materials. For example, the metasyntactic variables often used in Python literature are spam and eggs, instead of the traditional foo and bar.

Python is sometimes referred to as a "scripting language". In practice, it is used as a dynamic programming language for both application development and occasional scripting. Python has been used to develop many large software projects such as the Zope application server and the Mnet and BitTorrent file sharing systems. It is also extensively used by Google. [1]

Another important goal of the language is ease of extensibility. New built-in modules are easily written in C or C++. Python can also be used as an extension language for existing modules and applications that need a programmable interface.

Though the design of Python is somewhat hostile to functional programming (no tail call elimination or good support for anonymous closures) and the Lisp tradition, there are significant parallels between the philosophy of Python and that of minimalist Lisp-family languages such as Scheme. Many past Lisp programmers have found Python appealing for this reason.

3. duck typing

In computer science, duck typing is a term for dynamic typing typical of some programming languages, such as Smalltalk or Visual FoxPro, where a variable's value itself determines what the variable can do. It also implies that an object is interchangeable with any other object that implements the same interface, regardless of whether the objects have a related inheritance hierarchy.

The term is a reference to the "duck test"—"If it walks like a duck and quacks like a duck, it must be a duck." One can also say that the duck typing method ducks the issue of typing variables.

Pythonic programming style that determines an object's type by inspection of its method or attribute signature rather than by explicit relationship to some type object ("If it looks like a duck and quacks like a duck, it must be a duck.") By emphasizing interfaces rather than specific types, well-designed code improves its flexibility by allowing polymorphic substitution. Duck-typing avoids tests using type() or isinstance(). Instead, it typically employs hasattr() tests or EAFP [Easier to Ask Forgiveness than Permission] programming.

The standard example of duck typing in Python is file-like classes. Classes can implement some or all of the methods of file and can be used where file would normally be used. For example, GzipFile implements a file-like object for accessing gzip-compressed data. cStringIO allows treating a Python string as a file. Sockets and files share many of the same methods as well. However, sockets lack the tell() method and cannot be used everywhere that GzipFile can be used. This shows the flexibility of duck typing: a file-like object can implement only methods it is able to, and consequently it can be only used in situations where it makes sense.

4. 新名词Pythonic

A few neologisms have come into common use within the Python community. One of the most common is "pythonic", which can have a wide range of meanings related to program style. To say that a piece of code is pythonic is to say that it uses Python idioms well; that it is natural or shows fluency in the language. Likewise, to say of an interface or language feature that it is pythonic is to say that it works well with Python idioms; that its use meshes well with the rest of the language.

In contrast, a mark of unpythonic code is that it attempts to "write C++ (or Lisp, or Perl) code in Python"—that is, provides a rough transcription rather than an idiomatic translation of forms from another language.

The prefix Py- can be used to show that something is related to Python. Examples of the use of this prefix in names of Python applications or libraries include Pygame, a binding of SDL to Python (commonly used to create games), PyUI, a GUI encoded entirely in Python, and PySol, a series of solitaire card games programmed in Python.

Users and admirers of Python—most especially those considered knowledgeable or experienced—are often referred to as Pythonists, Pythonistas, and Pythoneers

5. Python支持的平台

The most popular (and therefore best maintained) platforms Python runs on are Linux, BSD, Mac OS X, Microsoft Windows. Separate implementations also exist for the Java (called Jython) and for the .NET Framework or Mono (called IronPython). Other supported platforms include:

Unix-like

Desktop OS's

Special and embedded

Mainframe and other

Most of the third-party libraries for Python (and even some first-party ones) are only available on Windows, Linux, BSD, and Mac OS X.

Python was originally developed as a scripting language for the Amoeba operating system capable of making system calls; however, that version is no longer maintained.

6. Python应用

The Python programming language is actively used in industry and academia for a wide variety of purposes.

6.1. Python的教育用途

As of 2005, Python is getting more popular for teaching computer programming. Its strengths for teaching include its syntactic simplicity, flexible typing, and interactive interpreter.

Python uses far fewer symbols than languages like Java and C. For example blocks inside loops and IF statements are indicated by indentation rather than curly braces ({}), and the end of a line does not have to have a semicolon. Beginning students often have initial trouble with memorizing where curly braces and semi-colons go. With Python students can skip directly to the fun part of writing code that does something. Similarly, with Java, and C++, variables types must be declared before being used. That is not needed in Python which again allows students to quickly get to the interesting part of getting their program to do something.

The interactive interpreter is an extremely valuable aid to learning and experimentation. Learning-by-doing is about trying things out and seeing what happens. The faster you can get results from your experiment, the faster that learning produces results. Experience has shown that the interactive interpreter and lack of a compiler really speeds up the learning process, both for beginners and for pros who are learning a new library and such.

6.2. 使用Python的大型组织

6.3. 使用Python写成的软件

6.4. Python包

The Python Cheese Shop and Vaults of Parnassus are two primary directories of hundreds of Python packages

See more recommended modules at Useful Modules in the Python.org wiki.

6.5. 软件目录

7. Python的实现

The standard Python interpreter also supports an interactive mode in which it acts as a kind of shell: expressions can be entered one at a time, and the result of their evaluation is seen immediately. This is a boon for those learning the language and experienced developers alike: snippets of code can be tested in interactive mode before integrating them into a proper program. As well, the Python shell is often used to interactively perform system tasks, such as modifying files.

Python also includes a unit testing framework for creating exhaustive test suites. While static typing aficionados see this as a replacement for a static type-checking system, Python programmers largely do not share this view.

Standard Python does not support continuations, and according to Guido van Rossum, never will. However, better support for coroutine-like functionality is planned, by extending Python's generators [3]

8. Python的标准库

Python has a large standard library, which makes it well suited to many tasks. This comes from a so-called "batteries included" philosophy for Python modules. The modules of the standard library can be augmented with custom modules written in either C or Python. The standard library is particularly well tailored to writing Internet-facing applications, with a large number of standard formats and protocols (such as MIME and HTTP) supported. Modules for creating graphical user interfaces, connecting to relational databases, arithmetic with arbitrarily precise decimals, and manipulating regular expressions are also included.

The standard library is one of Python's greatest strengths. The bulk of it is cross-platform compatible, meaning that even heavily leveraged Python programs can often run on Unix, Windows, Macintosh, and other platforms without change.

It is currently being debated whether or not third-party but open source Python modules such as Twisted, NumPy, or wxPython should be included in the standard library, in accordance with the batteries included philosophy.

9. Python学习资料

Python语法

Python was designed to be a highly readable language. It aims toward an uncluttered visual layout, uses English keywords frequently where other languages use punctuation, and has notably fewer syntactic constructions than many structured languages such as C, Perl, or Pascal.

1. Indentation

Python uses indentation, rather than curly braces, to delimit blocks. An increase in indentation comes after certain statements; a decrease in indentation signifies the end of the current block.

2. Statements

Python's statements include:

Each statement has its own semantics: for example, the def statement does not execute its block immediately, unlike most other statements.

3. Fundamental datatypes

Python includes a number of different datatypes. Amongst the most used are:

This list is not exhaustive; there are many other types provided by Python - these are merely some of the most commonly used.

Python使用技巧

1. Python的编码处理技术

对于中文用户，特别需要关注Python的编码技术. 列举一些常用的技巧。 

chr(i): 将一个0到255的整数转换为一个字符.
ord(c): 返回单个字符c的整数顺序值.普通字符返回[0,255]中的一个值,Unicode字符返回 [0,65535]中的一个值
unichr(i): 将一个0到65535的整数转换为一个Unicode字符

# -*- coding: UTF-8 -*-

sys.getdefaultencoding()

sys.setdefaultencoding('utf-8')

sys.getfilesystemencoding()

      sys.stdout.encoding

      sys.stdin.encoding

      unicode('abc', 'mbcs').encode('utf-8')

      'abc'.decode('mbcs').encode('utf-8')

2. Python常用模块

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