Python - ArchWiki

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Python - ArchWiki

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Python - ArchWiki

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Python arch wiki

  1. 1. Python - ArchWiki 1 of 6 Python From ArchWiki Python ( "is a remarkably powerful dynamic programming language that is used in a wide variety of application domains. Python is often compared to Tcl, Perl, Ruby, Scheme or Java." Related articles Python Package Guidelines mod_python Contents Python VirtualEnv 1 Installation 1.1 Python 3 1.2 Python 2 2 Dealing with version problem in build scripts 3 Integrated Development Environments 3.1 Eclipse 3.2 Eric 3.3 IEP 3.4 Ninja 3.5 Spyder 4 Getting easy_install 5 Getting completion in Python shell 6 Widget bindings 7 Old versions 8 More Resources 9 For Fun Installation There are currently two versions of Python: Python 3 (which is the default) and the older Python 2. Python 3 Python 3 is the latest version of the language, and is incompatible with Python 2. The language is mostly the same, but many details, especially how built-in objects like dictionaries and strings work, have changed considerably, and a lot of deprecated features have finally been removed. Also, the standard library has been reorganized in a few prominent places. For an overview of the differences, visit Python2orPython3 ( and their relevant chapter ( /diveintopython3/porting-code-to-python-3-with-2to3.html) in Dive into Python 3. To install the latest version of Python 3, install the python ( /?name=python) package from the official repositories. If you would like to build the latest RC/betas from source, visit Python Downloads ( /download/). The Arch User Repository also contains good PKGBUILDs. If you do decide to build the RC, note that the binary (by default) installs to /usr/local/bin/python3.x . 1/29/2014 12:40 PM
  2. 2. Python - ArchWiki 2 of 6 Python 2 To install the latest version of Python 2, install the python2 ( /?name=python2) package from the official repositories. Python 2 will happily run alongside Python 3. You need to specify python2 in order to run this version. Any program requiring Python 2 needs to point to /usr/bin/python2 , instead of /usr/bin/python , which points to Python 3. To do so, open the program or script in a text editor and change the first line. The line will show one of the following: #!/usr/bin/env python or #!/usr/bin/python In both cases, just change python to python2 and the program will then use Python 2 instead of Python 3. Another way to force the use of python2 without altering the scripts is to call it explicitely with python2, i.e. python2 Finally, you may not be able to control the script calls, but there is a way to trick the environment. It only works if the scripts use #!/usr/bin/env python , it won't work with #!/usr/bin/python . This trick relies on env searching for the first corresponding entry in the PATH variable. First create a dummy folder. $ mkdir ~/bin Then add a symlink 'python' to python2 and the config scripts in it. $ ln -s /usr/bin/python2 ~/bin/python $ ln -s /usr/bin/python2-config ~/bin/python-config Finally put the new folder at the beginning of your PATH variable. $ export PATH=~/bin:$PATH Note that this change is not permanent and is only active in the current terminal session. To check which python interpreter is being used by env , use the following command: $ which python A similar approach in tricking the environment, which also relies on #!/usr/bin/env python to be called by the script in question, is to use a Virtualenv. When a Virtualenv is activated, the Python executable pointed to by $PATH will be the one the Virtualenv was installed with. Therefore, if the Virtualenv is 1/29/2014 12:40 PM
  3. 3. Python - ArchWiki 3 of 6 installed with Python 2, python will refer to Python 2. To start, install python2-virtualenv ( # pacman -S python2-virtualenv Then create the Virtualenv. $ virtualenv2 venv # Creates a directory, venv/, containing the Virtualenv Activate the Virtualenv, which will update $PATH to point at Python 2. Note that this activation is only active for the current terminal session. $ source venv/bin/activate The desired script should then run using Python 2. Dealing with version problem in build scripts Many projects' build scripts assume python to be Python 2, and that would eventually result in an error typically complaining that print 'foo' is invalid syntax. Luckily, many of them call python in the $PATH instead of hardcoding #!/usr/bin/python in the shebang line, and the Python scripts are all contained within the project tree. So, instead of modifying the build scripts manually, there is an easy workaround. Just create /usr/local/bin/python with content like this: /usr/local/bin/python #!/bin/bash script=`readlink -f -- "$1"` case "$script" in (/path/to/project1/*|/path/to/project2/*|/path/to/project3*) exec python2 "$@" ;; esac script=`readlink -f -- "$2"` case "$script" in (/path/to/project1/*|/path/to/project2/*|/path/to/project3*) exec python2 "$@" ;; esac exec python3 "$@" Where /path/to/project1/*|/path/to/project2/*|/path/to/project3* is a list of patterns separated by | matching all project trees. Don't forget to make it executable: # chmod +x /usr/local/bin/python Afterwards scripts within the specified project trees will be run with Python 2. Integrated Development Environments 1/29/2014 12:40 PM
  4. 4. Python - ArchWiki 4 of 6 There are some IDEs for Python available in the official repositories. Eclipse Eclipse supports both Python 2.x and 3.x series by using the PyDev extension. Eric For the latest Python 3 compatible version, install the eric ( /?name=eric) package. Version 4 of Eric is Python 2 compatible and can be installed with the eric4 ( package. These IDEs can also handle Ruby. IEP IEP is an interactive (e.g. MATLAB) python IDE with basic debugging capabilities and is especially suitable for scientific computing. It is provided by the package iep ( /iep/). Ninja The Ninja IDE is provided by the package ninja-ide ( /?name=ninja-ide). Spyder Spyder (previously known as Pydee) is a powerful interactive development environment for the Python language with advanced editing, interactive testing, debugging and introspection features. It focuses on scientific computations, providing a matlab-like environment. It can be installed with the package spyder ( Getting easy_install The easy_install tool is available in the package python-setuptools ( /packages/?name=python-setuptools). Getting completion in Python shell Copy this into Python's interactive shell /usr/bin/python import rlcompleter import readline readline.parse_and_bind("tab: complete") 1/29/2014 12:40 PM
  5. 5. Python - ArchWiki 5 of 6 Source ( Widget bindings The following widget toolkit bindings are available: TkInter — Tk bindings || standard module pyQt — Qt bindings || python2-pyqt4 ( python2-pyqt5 ( python-pyqt4 ( python-pyqt5 ( pySide — Qt bindings || python2-pyside ( python-pyside ( pyGTK — GTK+ 2 bindings || pygtk ( PyGObject — GTK+ 2/3 bindings via GObject Introspection || python2-gobject2 ( /?name=python2-gobject2) python2-gobject ( /?name=python2-gobject) python-gobject2 ( /?name=python-gobject2) python-gobject ( /?name=python-gobject) wxPython — wxWidgets bindings || wxpython ( To use these with Python, you may need to install the associated widget kits. Old versions Old versions of Python are available via the AUR and may be useful for historical curiosity, old applications that don't run on current versions, or for testing Python programs intended to run on a distribution that comes with an older version (eg, RHEL 5.x has Python 2.4, or Ubuntu 12.04 has Python 3.1): python15 ( python16 python24 python25 python26 python30 Python 1.5.2 ( Python 1.6.1 ( Python 2.4.6 ( Python 2.5.6 ( Python 2.6.8 ( Python 3.0.1 1/29/2014 12:40 PM
  6. 6. Python - ArchWiki 6 of 6 python31 ( Python 3.1.5 python32 ( Python 3.2.3 As of November 2012, Python upstream only supports Python 2.6, 2.7, 3.1, 3.2, and 3.3 for security fixes. Using older versions for Internet-facing applications or untrusted code may be dangerous and is not recommended. Extra modules/libraries for old versions of Python may be found on the AUR by searching for python(version without decimal), eg searching for "python26" for 2.6 modules. More Resources Learning Python ( is one of the most comprehensive, up to date, and well-written books on Python available today. Dive Into Python ( is an excellent (free) resource, but perhaps for more advanced readers and has been updated for Python 3 ( A Byte of Python ( is a book suitable for users new to Python (and scripting in general). Learn Python The Hard Way ( the best intro to programming. ( nice site to learn python. Crash into Python ( Also known as Python for Programmers with 3 Hours, this guide gives experienced developers from other languages a crash course on Python. Beginning Game Development with Python and Pygame: From Novice to Professional ( for games For Fun Try the following snippets from Python's interactive shell: >>> import this >>> from __future__ import braces >>> import antigravity Retrieved from "" Category: Programming language This page was last modified on 25 January 2014, at 21:30. Content is available under GNU Free Documentation License 1.3 or later unless otherwise noted. 1/29/2014 12:40 PM