Python’s x% y returns a result with the sign of y instead, and may not be exactly computable for float arguments. For example, fmod(-1e-100, 1e100) is -1e-100, but the result of Python’s -1e-100% 1e100 is 1e100-1e-100, which cannot be represented exactly as a float, and rounds to the surprising 1e100. Ganglia is a scalable distributed monitoring system for high-performance computing systems such as clusters and Grids. It is based on a hierarchical design targeted at federations of clusters.
- PyPy is a Python 2.7/3.6/3.7 implementation utilizing a JIT compiler. It is generally faster and uses less memory, but is not fully compatible with CPython (although the majority of packages and code will work without any changes). Jython is a Python 2.7 implementation built in Java. It allows easy integration of Python and Java code, but is.
- The shortcut to the corresponding.exe automatically starts with Python 3.6.6, so I just have to switch spyder if I want to use another Python version. While this solution isn't very beautiful, it's enough for my purposes. – thomi Sep 2 '18 at 17:27.
is a wrapper script that opens a Python aware GUI editor. For this script to run, you must have installed Tk before Python so that the Tkinter Python module is built.
is the Python documentation tool.
is an interpreted, interactive, object-oriented programming language.
is a version-specific name for the python program.
creates virtual Python environments in one or more target directories.
From What is Python?:
- Python is an interpreted, interactive, object-oriented programming language. It incorporates modules, exceptions, dynamic typing, very high level dynamic data types, and classes. It supports multiple programming paradigms beyond object-oriented programming, such as procedural and functional programming. Python combines remarkable power with very clear syntax. It has interfaces to many system calls and libraries, as well as to various window systems, and is extensible in C or C++. It is also usable as an extension language for applications that need a programmable interface. Finally, Python is portable: it runs on many Unix variants including Linux and macOS, and on Windows.
Python 3 is the latest and actively developed version of the language. See What's New in Python to see the latest changes in Python 3.
To install the current release of Python 3, install the python package.
If you would like to build the latest RC/betas from source, visit Python Downloads. 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. As an alternative which does not require superuser capabilities and installs to the home directory, consider using pyenv.
Python 2 is an older version of the language. Python 3 and Python 2 are incompatible. For an overview of the differences, see the historical version of the Python2orPython3 document.
Although Python 2 is no longer actively maintained, there are some packages that still depend on it. Python 2 may also be useful for developers maintaining, using or porting legacy Python 2 software.
To get the latest version of Python 2, install the python2 package.
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 use
/usr/bin/python2, instead of
/usr/bin/python, which points to Python 3. However, many legacy Python 2 scripts incorrectly specify
python in their shebang line. To change this, open the program or script in a text editor and change the first line. The line may show one of the following:
In either case, change
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 explicitly with
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 will not work with
#!/usr/bin/python. This trick relies on
env searching for the first corresponding entry in the
First create a dummy folder:
Then add a symlink
python to python2 and the config scripts in it:
Finally put the new folder at the beginning of your
To check which python interpreter is being used by
env, use the following command:
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 virtual environment.
The python package installs CPython, the reference implementation of Python. However, there are also other implementations available. These implementations are usually based on older versions of Python and are not fully compatible with CPython.
Implementations available on Arch Linux include:
- PyPy — A Python implementation written in Python. It has speed and memory usage advantages compared to Cython.
- https://www.pypy.org pypy, pypy3
- Jython — An implementation of the Python language written in Java. It can be used to embed Python scripting into Java programs or use Java libraries in Python programs.
- http://www.jython.org/ jython
- micropython — Python for microcontrollers. It includes a small subset of the Python standard library and is optimized to run on microcontrollers and in constrained environments.
- https://micropython.org/ micropythonAUR
- IronPython — An implementation of the Python programming language which is tightly integrated with .NET. It can use .NET libraries and allows .NET programs to use Python libraries.
- https://ironpython.net ironpython-gitAUR
More implementations exist. Some, such as Stackless, Pyston and Cinder are used internally at large technology companies. Others are historically notable but are no longer maintained due to improvements in the most popular implementations.
The python package includes an interactive Python shell/REPL which can be launched with the
python command. The following shells are also available:
- bpython — A fancy interface for the Python interpreter.
- https://bpython-interpreter.org/ bpython
- IPython — A powerful interactive Python shell.
- https://ipython.org/ ipython
- Jupyter — A web-based computation application powered by IPython.
- https://jupyter.org/ jupyterlab, jupyter-notebook
- ptpython — An advanced Python REPL built with prompt-toolkit.
- https://github.com/jonathanslenders/ptpython ptpythonAUR
Old versions of Python are available via the AUR and may be useful for historical curiosity, old applications that do not run on current versions, or for testing Python programs intended to run on a distribution that comes with an older version:
- Python 3.8: python38AUR
- Python 3.7: python37AUR
- Python 3.6: python36AUR
- Python 3.5: python35AUR
- Python 3.4: python34AUR
Extra modules/libraries for old versions of Python may be found on the AUR by searching for
python<version without period>, e.g. searching for
python26 for 2.6 modules.
There are several ways to install Python packages on Arch Linux:
- Official repositories and AUR — A large number of popular packages are available in the Arch repositories. This is the preferred way to install system-wide packages.
- pip — The official package installer for Python. You can use pip to install packages from the Python Package Index and other indexes.
- https://pip.pypa.io/ python-pip
- Anaconda — An open source package management system and environment management system, originally created for Python programs. You can use Conda to install packages from the Anaconda repositories.
- https://docs.conda.io/projects/conda/ anacondaAUR
- Miniconda — A lightweight alternative to Anaconda which installs the package manager but does not install scientific computing packages by default.
- https://docs.conda.io/en/latest/miniconda.html miniconda3AUR
When installing packages from sources other than the official repositories and AUR, it is recommended to use a virtual environment (or Conda environment management) to prevent conflicts with system packages in
pip install --user can be used to install packages into the user scheme instead of
See the Python Packaging User Guide for the official best practices for package management.
Historically, easy_install (part of python-setuptools) was used to install packages distributed as Eggs. easy_install and Eggs have been replaced with pip and Wheels. See see pip vs easy_install and Wheel vs Egg for more information.
The following widget toolkit bindings are available:
- Tkinter — the standard Python interface to the Tk GUI toolkit
- https://docs.python.org/3/library/tkinter.html python
- Qt for Python (PySide2) — The official Python bindings for Qt
- https://www.qt.io/qt-for-python pyside2pyside2-tools
- pyQt — A set of Python bindings for Qt
- https://riverbankcomputing.com/software/pyqt/intro python-pyqt5
Python 3.6 Download
- PyGObject — Python bindings for GObject based libraries such as GTK, GStreamer, WebKitGTK, GLib, and GIO
- https://pygobject.readthedocs.io/ python-gobject
- wxPython — A cross-platform GUI toolkit for Python which wraps wxWidgets
- https://wxpython.org/ python-wxpython
To use these with Python, you may need to install the associated widget kits.
Tips and tricks
Python provides tools to create isolated virtual environments into which packages may be installed without conflicting with other virtual environments or the system packages. Virtual environments can also run applications with different versions of Python on the same system.
See Python/Virtual environment for details.
Tab completion in Python shell
Tab completion is available in the interactive shell by default. Note that the readline completer will only complete names in the global namespace. You can use python-jedi for a richer tab completion experience .
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