Using Python on Windows
This document aims to give an overview of Windows-specific behaviour you should know about when using Python on Microsoft Windows.
Installing Python
Unlike most Unix systems and services, Windows does not require Python natively and thus does not pre-install a version of Python. However, the CPython team has compiled Windows installers (MSI packages) with every release for many years.
With ongoing development of Python, some platforms that used to be supported earlier are no longer supported (due to the lack of users or developers). Check PEP 11 for details on all unsupported platforms.
- DOS and Windows 3.x are deprecated since Python 2.0 and code specific to these systems was removed in Python 2.1.
- Up to 2.5, Python was still compatible with Windows 95, 98 and ME (but already raised a deprecation warning on installation). For Python 2.6 (and all following releases), this support was dropped and new releases are just expected to work on the Windows NT family.
- Windows CE is still supported.
- The Cygwin installer offers to install the Python interpreter as well; it is located under “Interpreters.” (cf. Cygwin package source, Maintainer releases)
See Python for Windows (and DOS) for detailed information about platforms with precompiled installers.
See also
- Python on XP
- “7 Minutes to “Hello World!”” by Richard Dooling, 2006
- Installing on Windows
- in “Dive into Python: Python from novice to pro” by Mark Pilgrim, 2004, ISBN 1-59059-356-1
- For Windows users
- in “Installing Python” in “A Byte of Python” by Swaroop C H, 2003
Alternative bundles
Besides the standard CPython distribution, there are modified packages including additional functionality. The following is a list of popular versions and their key features:
- ActivePython
- Installer with multi-platform compatibility, documentation, PyWin32
- Python Enthought Edition
- Popular modules (such as PyWin32) with their respective documentation, tool suite for building extensible python applications
Notice that these packages are likely to install older versions of Python.
Configuring Python
In order to run Python flawlessly, you might have to change certain environment settings in Windows.
Excursus: Setting environment variables
Windows has a built-in dialog for changing environment variables (following guide applies to XP classical view): Right-click the icon for your machine (usually located on your Desktop and called “My Computer”) and choose Properties there. Then, open the Advanced tab and click the Environment Variables button.
In short, your path is:
My Computer ‣ Properties ‣ Advanced ‣ Environment Variables
In this dialog, you can add or modify User and System variables. To change System variables, you need non-restricted access to your machine (i.e. Administrator rights).
Another way of adding variables to your environment is using the set command:
set PYTHONPATH=%PYTHONPATH%;C:\My_python_lib
To make this setting permanent, you could add the corresponding command line to your autoexec.bat. msconfig is a graphical interface to this file.
Viewing environment variables can also be done more straight-forward: The command prompt will expand strings wrapped into percent signs automatically:
echo %PATH%
Consult set /? for details on this behaviour.
See also
- http://support.microsoft.com/kb/100843
- Environment variables in Windows NT
- http://support.microsoft.com/kb/310519
- How To Manage Environment Variables in Windows XP
- http://www.chem.gla.ac.uk/~louis/software/faq/q1.html
- Setting Environment variables, Louis J. Farrugia
Finding the Python executable
Besides using the automatically created start menu entry for the Python interpreter, you might want to start Python in the DOS prompt. To make this work, you need to set your %PATH% environment variable to include the directory of your Python distribution, delimited by a semicolon from other entries. An example variable could look like this (assuming the first two entries are Windows’ default):
C:\WINDOWS\system32;C:\WINDOWS;C:\Python25
Typing python on your command prompt will now fire up the Python interpreter. Thus, you can also execute your scripts with command line options, see Command line documentation.
Finding modules
Python usually stores its library (and thereby your site-packages folder) in the installation directory. So, if you had installed Python to C:\Python\, the default library would reside in C:\Python\Lib\ and third-party modules should be stored in C:\Python\Lib\site-packages\.
You can add folders to your search path to make Python’s import mechanism search in these directories as well. Use PYTHONPATH, as described in Environment variables, to modify sys.path. On Windows, paths are separated by semicolons, though, to distinguish them from drive identifiers (C:\ etc.).
Modifying the module search path can also be done through the Windows registry: Edit HKEY_LOCAL_MACHINE\SOFTWARE\Python\PythonCore\version\PythonPath\, as described above for the environment variable %PYTHONPATH%. A convenient registry editor is regedit (start it by typing “regedit” into Start ‣ Run).
Executing scripts
Python scripts (files with the extension .py) will be executed by python.exe by default. This executable opens a terminal, which stays open even if the program uses a GUI. If you do not want this to happen, use the extension .pyw which will cause the script to be executed by pythonw.exe by default (both executables are located in the top-level of your Python installation directory). This suppresses the terminal window on startup.
You can also make all .py scripts execute with pythonw.exe, setting this through the usual facilities, for example (might require administrative rights):
Launch a command prompt.
Associate the correct file group with .py scripts:
assoc .py=Python.File
Redirect all Python files to the new executable:
ftype Python.File=C:\Path\to\pythonw.exe "%1" %*
Additional modules
Even though Python aims to be portable among all platforms, there are features that are unique to Windows. A couple of modules, both in the standard library and external, and snippets exist to use these features.
The Windows-specific standard modules are documented in MS Windows Specific Services.
PyWin32
The PyWin32 module by Mark Hammond is a collection of modules for advanced Windows-specific support. This includes utilities for:
- Component Object Model (COM)
- Win32 API calls
- Registry
- Event log
- Microsoft Foundation Classes (MFC) user interfaces
PythonWin is a sample MFC application shipped with PyWin32. It is an embeddable IDE with a built-in debugger.
See also
- Win32 How Do I...?
- by Tim Golden
- Python and COM
- by David and Paul Boddie
Py2exe
Py2exe is a distutils extension (see Extending Distutils) which wraps Python scripts into executable Windows programs (*.exe files). When you have done this, you can distribute your application without requiring your users to install Python.
Compiling Python on Windows
If you want to compile CPython yourself, first thing you should do is get the source. You can download either the latest release’s source or just grab a fresh checkout.
For Microsoft Visual C++, which is the compiler with which official Python releases are built, the source tree contains solutions/project files. View the readme.txt in their respective directories:
Directory | MSVC version | Visual Studio version |
---|---|---|
PC/VC6/ | 6.0 | 97 |
PC/VS7.1/ | 7.1 | 2003 |
PC/VS8.0/ | 8.0 | 2005 |
PCbuild/ | 9.0 | 2008 |
Note that not all of these build directories are fully supported. Read the release notes to see which compiler version the official releases for your version are built with.
Check PC/readme.txt for general information on the build process.
For extension modules, consult Building C and C++ Extensions on Windows.
See also
- Python + Windows + distutils + SWIG + gcc MinGW
- or “Creating Python extensions in C/C++ with SWIG and compiling them with MinGW gcc under Windows” or “Installing Python extension with distutils and without Microsoft Visual C++” by Sébastien Sauvage, 2003
- MingW – Python extensions
- by Trent Apted et al, 2007
Other resources
See also
- Python Programming On Win32
- “Help for Windows Programmers” by Mark Hammond and Andy Robinson, O’Reilly Media, 2000, ISBN 1-56592-621-8
- A Python for Windows Tutorial
- by Amanda Birmingham, 2004