Python (programming language) explained

Python
Paradigm:multi-paradigm

object-oriented, imperative, functional, procedural, reflective

Year:1991
Designer:Guido van Rossum
Developer:Python Software Foundation
Latest Release Version:3.2.2 /

2.7.2 /
Latest Preview Version:3.3.0a1 /
[1]
Typing:duck, dynamic, strong
Implementations:CPython, IronPython, Jython, Python for S60, PyPy
Dialects:Cython, RPython, Stackless Python
Influenced By:ABC, ALGOL 68,[2] C,[3] C++, [4] Dylan,[5] Haskell,[6] Icon,[7] Java,[8] Lisp, Modula-3, Perl
Influenced:Boo, Cobra, D, Falcon, Groovy, JavaScript, Ruby[9]
Operating System:Cross-platform
License:Python Software Foundation License
Website:python.org
File Ext:.py, .pyw, .pyc, .pyo, .pyd
Wikibooks:Python Programming

Python is a general-purpose, high-level programming language[10] whose design philosophy emphasizes code readability.[11] Python claims to combine "remarkable power with very clear syntax",[12] and its standard library is large and comprehensive.

Python supports multiple programming paradigms, primarily but not limited to object-oriented, imperative and, to a lesser extent, functional programming styles. It features a fully dynamic type system and automatic memory management, similar to that of Scheme, Ruby, Perl, and Tcl. Like other dynamic languages, Python is often used as a scripting language, but is also used in a wide range of non-scripting contexts. Using third-party tools, Python code can be packaged into standalone executable programs. Python interpreters are available for many operating systems.

The reference implementation of Python (CPython) is free and open source software and has a community-based development model, as do all or nearly all of its alternative implementations. CPython is managed by the non-profit Python Software Foundation.

History

See main article: History of Python.

Python was conceived in the late 1980s[13] and its implementation was started in December 1989[14] by Guido van Rossum at CWI in the Netherlands as a successor to the ABC programming language (itself inspired by SETL)[15] capable of exception handling and interfacing with the Amoeba operating system.[16] Van Rossum is Python's principal author, and his continuing central role in deciding the direction of Python is reflected in the title given to him by the Python community, Benevolent Dictator for Life (BDFL).

Python 2.0 was released on 16 October 2000, with many major new features including a full garbage collector and support for Unicode. However, the most important change was to the development process itself, with a shift to a more transparent and community-backed process.[17] Python 3.0 (also known as Python 3000 or py3k), a major, backwards-incompatible release, was released on 3 December 2008[18] after a long period of testing. Many of its major features have been backported to the backwards-compatible Python 2.6 and 2.7.[19] Python has been awarded a TIOBE Programming Language of the Year award twice (2007, 2010), which is given to the language with the greatest growth in popularity over the course of the year (as measured by the TIOBE index).[20]

Programming philosophy

Python is a multi-paradigm programming language. Rather than forcing programmers to adopt a particular style of programming, it permits several styles: object-oriented programming and structured programming are fully supported, and there are a number of language features which support functional programming and aspect-oriented programming (including by metaprogramming[21] and by magic methods).[22] Many other paradigms are supported using extensions, such as pyDBC[23] and Contracts for Python[24] which allow design by contract.

Python uses dynamic typing and a combination of reference counting and a cycle-detecting garbage collector for memory management. An important feature of Python is dynamic name resolution (late binding), which binds method and variable names during program execution.

Rather than requiring all desired functionality to be built into the language's core, Python was designed to be highly extensible. New built-in modules can be easily written in C, C++ or Cython. Python can also be used as an extension language for existing modules and applications that need a programmable interface. This design of a small core language with a large standard library and an easily extensible interpreter was intended by Van Rossum from the very start because of his frustrations with ABC (which espoused the opposite mindset).[13]

The design of Python offers only limited support for functional programming in the Lisp tradition. However, Python's design philosophy exhibits significant similarities to those of minimalistic Lisp-family languages, such as Scheme. The language has map, reduce and filter functions, and the list comprehensions added in Python 2.0 have since been extended with comprehensions for dictionaries and sets, as well as generator expressions. The standard library has two modules (itertools and functools) that implement functional tools borrowed from Haskell and Standard ML.[25]

While offering choice in coding methodology, the Python philosophy rejects exuberant syntax, such as in Perl, in favor of a sparser, less-cluttered grammar. 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". As Alex Martelli put it in his Python Cookbook (2nd ed., p. 230): "To describe something as clever is NOT considered a compliment in the Python culture." Python's philosophy rejects the Perl "there is more than one way to do it" approach to language design in favor of "there should be one—and preferably only one—obvious way to do it".[26]

Python's developers eschew premature optimization, and moreover, reject patches to non-critical parts of CPython which would offer a marginal increase in speed at the cost of clarity.[27] When speed is important, Python programmers tend to try using a JIT compiler such as Psyco or using an alternative language implementation such as PyPy. When pure Python code is not fast enough, time-critical functions can be rewritten in "closer to the metal" languages such as C, or by translating (a dialect of) Python code to C code using tools like Cython.[28]

The core philosophy of the language is summarized by the document "PEP 20 (The Zen of Python)".[26]

Name and neologisms

An important goal of the Python developers is making Python fun to use. This is reflected in the origin of the name (derived from 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.[29] [30] For example, the metasyntactic variables often used in Python literature are spam and eggs,[29] [31] instead of the traditional foo and bar.

A common neologism in the Python community is pythonic, which can have a wide range of meanings related to program style. To say that 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, Perl, or Java) code in Python—that is, provides a rough transcription rather than an idiomatic translation of forms from another language. The concept of pythonicity is tightly bound to Python's minimalist philosophy of readability and avoiding the "there's more than one way to do it" approach. Unreadable code or incomprehensible idioms are unpythonic.

Users and admirers of Python—most especially those considered knowledgeable or experienced—are often referred to as Pythonists, Pythonistas, and Pythoneers.[32]

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); PyS60, an implementation for the Symbian Series 60 Operating System; PyQt and PyGTK, which bind Qt and GTK, respectively, to Python; and PyPy, a Python implementation written in Python. The prefix is also used outside of naming software packages: the major Python conference is named PyCon.

Usage

See main article: Python software.

Python is often used as a scripting language for web applications, e.g. via mod_wsgi for the Apache web server. With Web Server Gateway Interface, a standard API has been developed to facilitate these applications. Web application frameworks like Django, Pylons, TurboGears, web2py, Tornado, Flask and Zope support developers in the design and maintenance of complex applications. Libraries like NumPy, SciPy and Matplotlib allow Python to be used effectively in scientific computing.

Python has been successfully embedded in a number of software products as a scripting language, including in finite element method software such as Abaqus, 3D animation packages such as Blender, Cinema 4D, Lightwave, Houdini, Maya, modo, MotionBuilder, Softimage, the visual effects compositor Nuke, and 2D imaging programs like GIMP, Inkscape, Scribus and Paint Shop Pro.[33] GNU GDB uses Python as a pretty printer to show complex structures such as C++ containers. ESRI is now promoting Python as the best choice for writing scripts in ArcGIS.[34] It has even been used in several video games,[35] [36] and has been adopted as first of the three available programming languages in Google App Engine, the other two being Java and Go.[37]

Thanks to being a scripting language with module architecture, syntax simplicity and rich text processing tools, Python is often used for Natural language processing tasks. Python has also been used in Artificial Intelligence tasks[38] [39] [40] .

For many operating systems, Python is a standard component; it ships with most Linux distributions, FreeBSD, NetBSD, OpenBSD and with Mac OS X and can be used from the terminal. A number of Linux distributions use installers written in Python: Ubuntu uses the Ubiquity installer, while Red Hat Linux and Fedora use the Anaconda installer. Gentoo Linux uses Python in its package management system, Portage and the standard tool to access it, emerge. Pardus uses it for administration and during system boot.[41]

Python has also seen extensive use in the information security industry, including exploit development.[42] [43]

Among the users of Python are YouTube[44] and the original BitTorrent client.[45] Large organizations that make use of Python include Google,[44] Yahoo!,[46] CERN,[47] NASA,[48] ILM,[49] and ITA.[50] Most of the Sugar software for the One Laptop per Child XO, now developed at Sugar Labs, is written in Python.[51]

In addition to standard desktop Python IDEs, there are also browser-based IDEs, such as NCLab and Sage, intended for developing science and math-related Python programs.

Syntax and semantics

See main article: Python syntax and semantics.

Python is intended to be a highly readable language. It is designed to have an uncluttered visual layout, frequently using English keywords where other languages use punctuation. Python requires less boilerplate than traditional manifestly typed structured languages such as C or Pascal, and has a smaller number of syntactic exceptions and special cases than either of these.[52] For a detailed description of the differences between 2.x and 3.x versions, see History of Python.

The simplicity of Python is demonstrated by its version of the classic "Hello world" program:print("Hello world")

Indentation

Python uses whitespace indentation, rather than curly braces or keywords, to delimit blocks (a feature also known as the off-side rule). An increase in indentation comes after certain statements; a decrease in indentation signifies the end of the current block.[53]

Statements and control flow

Python's statements include (among others):

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

Python does not support first-class continuations, and according to Guido van Rossum it never will.[54] However, better support for coroutine-like functionality is provided in 2.5, by extending Python's generators.[55] Prior to 2.5, generators were lazy iterators; information was passed unidirectionally out of the generator. As of Python 2.5, it is possible to pass information back into a generator function.

Expressions

Python expressions are similar to languages such as C and Java.

In Python, a distinction between expressions and statements is rigidly enforced, in contrast to languages such as Common Lisp, Scheme, or Ruby. This leads to some duplication of functionality, e.g.

Statements cannot be a part of an expression and so list and other comprehensions or lambda expressions, all being expressions, cannot contain statements. A particular case of this is that an assignment statement such as a = 1 cannot form part of the conditional expression of a conditional statement. This has the advantage of avoiding a classic C error of mistaking an assignment operator = for an equality operator == in conditions: if (c = 1) { ... } is valid C code but if c = 1: ... causes a syntax error in Python.

Methods

Methods on objects are functions attached to the object's class; the syntax instance.method(argument) is, for normal methods and functions, syntactic sugar for Class.method(instance, argument). Python methods have an explicit [[This (computer science)|self]] parameter to access instance data, in contrast to the implicit self in some other object-oriented programming languages (for example, Java, C++ or Ruby).[58]

Typing

Python uses duck typing and has typed objects but untyped variable names. Type constraints are not checked at compile time; rather, operations on an object may fail, signifying that the given object is not of a suitable type. Despite being dynamically typed, Python is strongly typed, forbidding operations that are not well-defined (for example, adding a number to a string) rather than silently attempting to make sense of them.

Python allows programmers to define their own types using classes, which are most often used for object-oriented programming. New instances of classes are constructed by calling the class (for example, SpamClass or EggsClass), and the classes themselves are instances of the metaclass type (itself an instance of itself), allowing metaprogramming and reflection.

Prior to version 3.0, Python had two kinds of classes: "old-style" and "new-style".[59] Old-style classes were eliminated in Python 3.0, making all classes new-style. In versions between 2.2 and 3.0, both kinds of classes could be used. The syntax of both styles is the same, the difference being whether the class object is inherited from, directly or indirectly (all new-style classes inherit from object and are instances of type).

Here is a summary of Python 3's built-in types:

TypeDescriptionSyntax example
[[String (computer science)|str]]An immutable sequence of Unicode codepoints.'Wikipedia'
"Wikipedia"
"""Spanning<br />multiple<br />lines"""
bytearrayA mutable sequence of bytesbytearray(b'Some ASCII')<code><br /><code>bytearray(b"Some ASCII")
[[byte]]sAn immutable sequence of bytesb'Some ASCII'<code><br /><code>b"Some ASCII"
[[list (computer science)|list]]Mutable, can contain mixed types[4.0, 'string', True]
[[tuple]]Immutable, can contain mixed types(4.0, 'string', True)
[[set (computer science)|set]], frozensetUnordered, contains no duplicates. A frozenset is immutable.{4.0, 'string', True}
frozenset([4.0, 'string', True])
[[associative array|dict]]A mutable group of key and value pairs{'key1': 1.0, 3: False}
[[integer (computer science)|int]]An immutable integer of unlimited magnitude.[60] 42
[[floating point|float]]An immutable floating point number (system-defined precision)3.1415927
[[complex number|complex]]An immutable complex number with real and imaginary parts3+2.7j
[[truth value|bool]]An immutable truth valueTrue
False

Mathematics

In contrast with some programming languages, integer division is defined to round towards minus infinity. Therefore 7 // 3 is 2, but (−7) // 3 is −3. This is uniform and consistent: for instance, it means that the equation (a+b) // b == a // b + 1 is always true, whereas in languages such as C, (-6+7) // 7 == -6 // 7. It also means that the equation b * (a // b) + a % b == a is valid for both positive and negative values of a. However, maintaining the validity of this equation means that while the result of a % b is, as expected, in the half-open interval [0,''b''), where <code>b</code> is a positive integer, it has to lie in the interval (''b'',0] when b is negative. [61]

Python provides a round function for rounding floats to integers. Versions before 3 use round-away-from-zero: round(0.5) is 1.0, round(-0.5) is -1.0.[62] Python 3 uses round-to-even: round(1.5) is 2.0, round(2.5) is 2.0.[63] The Decimal type/class in module decimal (since version 2.4) provides exact numerical representation and several rounding modes.

Python allows boolean expressions with multiple equality relations in a manner that is consistent with general usage in mathematics. For example, the expression a < b < c tests whether a is less than b and b is less than c. C-derived languages interpret this expression differently: in C, the expression would first evaluate a < b, resulting in 0 or 1, and that result would then be compared with c.[64]

Implementations

CPython

See main article: CPython.

The mainstream Python implementation, known as CPython, is written in C meeting the C89 standard.[65] CPython compiles Python programs into intermediate bytecode,[66] which are then executed by the virtual machine.[67] It is distributed with a large standard library written in a mixture of C and Python. CPython ships in versions for many platforms, including Microsoft Windows and most modern Unix-like systems. CPython was intended from almost its very conception to be cross-platform; its use and development on esoteric platforms such as Amoeba, alongside more conventional ones like Unix and Mac OS, has greatly helped in this regard.[68]

Stackless Python is a significant fork of CPython that implements microthreads; it does not use the C memory stack. It can be expected to run on approximately the same platforms that CPython runs on.

Google started a project called Unladen Swallow in 2009 with the aims of increasing the speed of the Python interpreter by 5 times by using the LLVM and improving its multithreading ability to scale to thousands of cores.[69] Later the project lost Google's backing and its main developers., the project hasn't achieved its goal; the modified interpreter is only about 2 times faster.

Alternative implementations

Jython compiles the Python program into Java byte code, which can then be executed by every Java Virtual Machine implementation. This also enables the use of Java class library functions from the Python program. IronPython follows a similar approach in order to run Python programs on the .NET Common Language Runtime. PyPy is a fast self-hosting implementation of Python, written in Python, that can output several types of bytecode, object code and intermediate languages. There also exist compilers to high-level object languages, with either unrestricted Python, a restricted subset of Python, or a language similar to Python as the source language. PyPy is of this type, compiling RPython to several languages; other examples include Pyjamas compiling to JavaScript; Shed Skin compiling to C++; and Cython and Pyrex compiling to C.

In 2005 Nokia released a Python interpreter for the Series 60 mobile phones called PyS60. It includes many of the modules from the CPython implementations and some additional modules for integration with the Symbian operating system. This project has been kept up to date to run on all variants of the S60 platform and there are several third party modules available. The Nokia N900 also supports Python with gtk widget libraries, with the feature that programs can be both written and run on the device itself. There is also a Python interpreter for Windows CE devices (including Pocket PC). It is called PythonCE.[70] There are additional tools available for easy application and GUI development.

The PyMite virtual machine began in 2000 and made its first public appearance at PyCon 2003.[71] PyMite was folded into Python-on-a-Chip in 2009.[72] Python-on-a-Chip (p14p) is a project to develop a reduced Python virtual machine (codenamed PyMite) that runs a significant subset of the Python language on microcontrollers without an OS in as little as 4KB of RAM.[73]

Around 2004, the Pyastra project created a specialized translator and assembler that targets resource-constrained microcontrollers.

ChinesePython (中蟒) is a Python programming language using a Chinese-language lexicon. Besides reserved words and variable names, most data type operations can be coded in Chinese as well.

Python is available on Android as an option as part of the Android Scripting Environment.[74]

Interpretational semantics

Most Python implementations (including CPython) can function as a command line interpreter, for which the user enters statements sequentially and receives the results immediately. In short, Python acts as a shell. While the semantics of the other modes of execution (bytecode compilation, or compilation to native code) preserve the sequential semantics, they offer a speed boost at the cost of interactivity, so they are usually only used outside of a command-line interaction (e.g., when importing a module).

Other shells add capabilities beyond those in the basic interpreter, including IDLE and IPython. While generally following the visual style of the Python shell, they implement features like auto-completion, retention of session state, and syntax highlighting.

Some implementations can compile not only to bytecode, but can turn Python code into machine code. So far, this has only been done for restricted subsets of Python. PyPy takes this approach, naming its restricted compilable version of Python RPython.

Psyco is a specialising just in time compiler that integrates with CPython and transforms bytecode to machine code at runtime. The produced code is specialised for certain data types and is faster than standard Python code. Psyco is compatible with all Python code, not only a subset.[75]

Development

Python's development is conducted largely through the Python Enhancement Proposal (PEP) process. PEPs are standardized design documents providing general information related to Python, including proposals, descriptions, design rationales, and explanations for language features.[76] Outstanding PEPs are reviewed and commented upon by Van Rossum, the Python project's Benevolent Dictator for Life (leader / language architect).[77] CPython's developers also communicate over a mailing list, python-dev, which is the primary forum for discussion about the language's development; specific issues are discussed in the Roundup bug tracker maintained at python.org.[78] Development takes place at the self-hosted hg.python.org.

CPython's public releases come in three types, distinguished by which part of the version number is incremented:

A number of alpha, beta, and release-candidates are also released as previews and for testing before the final release is made. Although there is a rough schedule for each release, this is often pushed back if the code is not ready. The development team monitor the state of the code by running the large unit test suite during development, and using the BuildBot continuous integration system.[81]

Standard library

Python has a large standard library, commonly cited as one of Python's greatest strengths,[82] providing pre-written tools suited to many tasks. This is deliberate and has been described as a "batteries included"[83] Python philosophy. The modules of the standard library can be augmented with custom modules written in either C or Python. Boost C++ Libraries includes a library, Boost.Python, to enable interoperability between C++ and Python. Because of the wide variety of tools provided by the standard library, combined with the ability to use a lower-level language such as C and C++, which is already capable of interfacing between other libraries, Python can be a powerful glue language between languages and tools.

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) already supported. Modules for creating graphical user interfaces, connecting to relational databases, arithmetic with arbitrary precision decimals, manipulating regular expressions, and doing unit testing are also included.[84]

Some parts of the standard library are covered by specifications (for example, the WSGI implementation wsgiref follows PEP 333[85]), but the majority of the modules are not. They are specified by their code, internal documentation, and test suite (if supplied). However, because most of the standard library is cross-platform Python code, there are only a few modules that must be altered or completely rewritten by alternative implementations.

The standard library is not essential to run Python or embed Python within an application. Blender 2.49 for instance omits most of the standard library.

For software testing, the standard library provides the unittest and [[doctest]] modules.

Influence on other languages

Python's design and philosophy have influenced several programming languages, including:

Notes and References

  1. Web site: Python 3.3.0 Release. Python Software Foundation. 5 March 2012. 12 March 2012.
  2. Web site: Interview with Guido van Rossum (July 1998). Kuchling. Andrew M.. amk.ca. 22 December 2006. 12 March 2012.
  3. van Rossum. Guido. 1993. An Introduction to Python for UNIX/C Programmers. Proceedings of the NLUUG najaarsconferentie (Dutch UNIX users group). even though the design of C is far from ideal, its influence on Python is considerable..
  4. Web site: Classes. The Python Tutorial. Python Software Foundation. 2012-02-20. It is a mixture of the class mechanisms found in C++ and Modula-3.
  5. Web site: The Python 2.3 Method Resolution Order. Simionato. Michele. Python Software Foundation. The C3 method itself has nothing to do with Python, since it was invented by people working on Dylan and it is described in a paper intended for lispers.
  6. Web site: Functional Programming HOWTO. Kuchling. A. M.. Python v2.7.2 documentation. Python Software Foundation. 2012-02-09.
  7. Web site: PEP 255 -- Simple Generators. Neil. Schemenauer. Tim. Peters. Magnus Lie. Hetland. 2001-05-18. Python Enhancement Proposals. Python Software Foundation. 2012-02-09.
  8. Web site: PEP 318 -- Decorators for Functions and Methods. Kevin D.. Smith. Jim J.. Jewett. Skip. Montanaro. Anthony. Baxter. 2 September 2004. Python Enhancement Proposals. Python Software Foundation. 24 February 2012.
  9. Book: Bini, Ola. Practical JRuby on Rails Web 2.0 Projects: bringing Ruby on Rails to the Java platform. 2007. APress. Berkeley. 978-1-59059-881-8. 3.
  10. Web site: What is Python Good For?. General Python FAQ. Python Software Foundation. 2008-09-05.
  11. Web site: What is Python? Executive Summary. Python Essays. Python Software Foundation. 2007-03-21.
  12. Web site: What is Python?. General Python FAQ. Python Software Foundation. 2009-06-27.
  13. Web site: The Making of Python. Venners. Bill. 2003-01-13. Artima Developer. Artima. 2007-03-22.
  14. Web site: A Brief Timeline of Python. van Rossum. Guido. 2009-01-20. The History of Python. Google. 2009-01-20.
  15. SETL (was: Lukewarm about range literals). 2000-08-29. 2011-03-13. Python-Dev. van Rossum. Guido. Guido van Rossum.
  16. Web site: Why was Python created in the first place?. General Python FAQ. Python Software Foundation. 2007-03-22.
  17. Web site: What's New in Python 2.0. Kuchling. A. M.. Zadka. Moshe. 2000-10-16. Python Software Foundation. 2012-02-11.
  18. Web site: Python 3.0 Release. Python Software Foundation. 2009-07-08.
  19. Web site: PEP 3000 -- Python 3000. van Rossum. Guido. 2006-04-05. Python Enhancement Proposals. Python Software Foundation. 2009-06-27.
  20. Web site: TIOBE Programming Community Index for March 2012. March 2012. TIOBE Software. 2012-03-25.
  21. Web site: Python Metaclasses: Who? Why? When?. http://www.webcitation.org/5lubkaJRc. 2009-12-10. PDF. The Cain Gang Ltd.. 2009-06-27.
  22. Web site: 3.3. Special method names. The Python Language Reference. Python Software Foundation. 2009-06-27.
  23. Web site: PyDBC: method preconditions, method postconditions and class invariants for Python. 24 September 2011.
  24. Web site: Contracts for Python. 24 September 2011.
  25. Web site: 6.5 itertools - Functions creating iterators for efficient looping. Docs.python.org. 2008-11-24.
  26. Web site: PEP 20 -- The Zen of Python. Peters. Tim. 2004-08-19. Python Enhancement Proposals. Python Software Foundation. 2008-11-24.
  27. http://www.python.org/dev/culture/ Python Culture
  28. Web site: Python Patterns - An Optimization Anecdote. Python Essays. Python Software Foundation. 2012-02-19.
  29. Web site: Whetting Your Appetite. The Python Tutorial. Python Software Foundation. 2012-02-20.
  30. Web site: Learn Python the Hard Way. Shaw. Zed A.. learnpythonthehardway.org. 2012-02-20.
  31. Web site: In Python, should I use else after a return in an if block?. 2011-02-17. Stack Overflow. Stack Exchange. 2011-05-06.
  32. Web site: Code Like a Pythonista: Idiomatic Python. David Goodger.
    Web site: How to think like a Pythonista.
  33. Documentation of the PSP Scripting API can be found at JASC Paint Shop Pro 9: Additional Download Resources
  34. Web site: About getting started with writing geoprocessing scripts. 2006-11-17. ArcGIS Desktop Help 9.2. Environmental Systems Research Institute. 2012-02-11.
  35. Web site: Stackless Python 2.5. CCP Games. 2007-07-23. porkbelly. Eve Insider Dev Blog. As you may well know, your favorite space-game owes its existence to the programming language Python. http://www.webcitation.org/5ru5w3vSR. 2010-08-10.
  36. Web site: Modding Sid Meier's Civilization IV. Caudill. Barry. 2005-09-20. Firaxis Games. http://www.webcitation.org/5ru5VItfv. 2010-08-10. Sid Meier's Civilization IV Developer Blog. we created three levels of tools ... The next level offers Python and XML support, letting modders with more experience manipulate the game world and everything in it..
  37. Web site: Python Language Guide (v1.0). Google Documents List Data API v1.0. Google. http://www.webcitation.org/5ru5FHxfV. 2010-08-10.
  38. Paine. Jocelyn. AI in Python. AI Expert Newsletter. Amzi!. 2005. August. 2012-02-11.
  39. Web site: PyAIML 0.8.5 - An interpreter package for AIML, the Artificial Intelligence Markup Language. Stratton. Cort. Python Software Foundation. 2012-02-11.
  40. Book: Artificial Intelligence: A Modern Approach. Russell. Stuart J.. Stuart J. Russell. Norvig. Peter. Peter Norvig. y. 3rd. 2009. Prentice Hall. Upper Saddle River, NJ. 978-0-13-604259-4. 1062. 2012-02-11.
  41. Web site: Pardus: TÜBİTAK]/UEKAE]. pardus.org.tr. 2008-11-24.
  42. Web site: Welcome to Immunity Debugger. Immunity. 2008-11-24.
    Web site: CORE Security Technologies' open source software repository. Core Security Technologies. 2012-02-11.
  43. Web site: Wapiti - Web application vulnerability scanner / security auditor. Surribas. Nicolas. SourceForge. 2008-11-24.
  44. Web site: Quotes about Python. Python Software Foundation. 2012-01-08.
  45. Web site: BitTorrent Style. Figgins. Stephen. 17 July 2003. ONLamp.com. O'Reilly Media. 24 September 2011.
  46. Web site: Organizations Using Python. Python Software Foundation. 2009-01-15.
  47. Python : the holy grail of programming. CERN Bulletin. 31/2006. CERN Publications. 2006-07-31. 2012-02-11.
  48. Web site: Python Streamlines Space Shuttle Mission Design. Shafer. Daniel G.. 2003-01-17. Python Software Foundation. 2008-11-24.
  49. Web site: Industrial Light & Magic Runs on Python. Fortenberry. Tim. 2003-01-17. Python Software Foundation. 2012-02-11.
  50. Web site: Python Slithers into Systems. Taft. Darryl K.. 5 March 2007. eWeek.com. Ziff Davis Holdings. 24 September 2011.
  51. Web site: What is Sugar?. Sugar Labs. 2012-02-11.
  52. Web site: Is Python a good language for beginning programmers?. General Python FAQ. Python Software Foundation. 2007-03-21.
  53. Web site: Myths about indentation in Python. Secnetix.de. 2011-04-19.
  54. Web site: Language Design Is Not Just Solving Puzzles. Guido. van Rossum. 9 February 2006. 21 March 2007. Artima forums. Artima.
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