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.. highlightlang:: none
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Using Python on Windows
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.. sectionauthor:: Robert Lehmann <lehmannro@gmail.com>
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This document aims to give an overview of Windows-specific behaviour you should
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know about when using Python on Microsoft Windows.
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Unlike most Unix systems and services, Windows does not require Python natively
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and thus does not pre-install a version of Python. However, the CPython team
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has compiled Windows installers (MSI packages) with every `release
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<https://www.python.org/download/releases/>`_ for many years.
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With ongoing development of Python, some platforms that used to be supported
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earlier are no longer supported (due to the lack of users or developers).
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Check :pep:`11` for details on all unsupported platforms.
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* DOS and Windows 3.x are deprecated since Python 2.0 and code specific to these
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systems was removed in Python 2.1.
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* Up to 2.5, Python was still compatible with Windows 95, 98 and ME (but already
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raised a deprecation warning on installation). For Python 2.6 (and all
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following releases), this support was dropped and new releases are just
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expected to work on the Windows NT family.
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* `Windows CE <http://pythonce.sourceforge.net/>`_ is still supported.
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* The `Cygwin <https://cygwin.com/>`_ installer offers to install the Python
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interpreter as well (cf. `Cygwin package source
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<ftp://ftp.uni-erlangen.de/pub/pc/gnuwin32/cygwin/mirrors/cygnus/
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release/python>`_, `Maintainer releases
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<http://www.tishler.net/jason/software/python/>`_)
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See `Python for Windows (and DOS) <https://www.python.org/download/windows/>`_
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for detailed information about platforms with precompiled installers.
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`Python on XP <http://dooling.com/index.php/2006/03/14/python-on-xp-7-minutes-to-hello-world/>`_
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"7 Minutes to "Hello World!""
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by Richard Dooling, 2006
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`Installing on Windows <http://www.diveintopython.net/installing_python/windows.html>`_
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in "`Dive into Python: Python from novice to pro
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<http://www.diveintopython.net/>`_"
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by Mark Pilgrim, 2004,
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`For Windows users <http://python.swaroopch.com/installation.html#installation-on-windows>`_
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in "Installing Python"
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in "`A Byte of Python <http://python.swaroopch.com/>`_"
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Besides the standard CPython distribution, there are modified packages including
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additional functionality. The following is a list of popular versions and their
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`ActivePython <https://www.activestate.com/activepython/>`_
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Installer with multi-platform compatibility, documentation, PyWin32
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`Enthought Python Distribution <https://www.enthought.com/products/epd/>`_
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Popular modules (such as PyWin32) with their respective documentation, tool
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suite for building extensible Python applications
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Notice that these packages are likely to install *older* versions of Python.
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In order to run Python flawlessly, you might have to change certain environment
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Excursus: Setting environment variables
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---------------------------------------
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Windows has a built-in dialog for changing environment variables (following
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guide applies to XP classical view): Right-click the icon for your machine
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(usually located on your Desktop and called "My Computer") and choose
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:menuselection:`Properties` there. Then, open the :guilabel:`Advanced` tab
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and click the :guilabel:`Environment Variables` button.
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In short, your path is:
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:menuselection:`My Computer
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--> Environment Variables`
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In this dialog, you can add or modify User and System variables. To change
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System variables, you need non-restricted access to your machine
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(i.e. Administrator rights).
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Another way of adding variables to your environment is using the :command:`set`
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set PYTHONPATH=%PYTHONPATH%;C:\My_python_lib
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To make this setting permanent, you could add the corresponding command line to
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your :file:`autoexec.bat`. :program:`msconfig` is a graphical interface to this
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Viewing environment variables can also be done more straight-forward: The
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command prompt will expand strings wrapped into percent signs automatically::
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Consult :command:`set /?` for details on this behaviour.
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https://support.microsoft.com/kb/100843
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Environment variables in Windows NT
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https://support.microsoft.com/kb/310519
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How To Manage Environment Variables in Windows XP
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https://www.chem.gla.ac.uk/~louis/software/faq/q1.html
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Setting Environment variables, Louis J. Farrugia
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Finding the Python executable
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-----------------------------
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Besides using the automatically created start menu entry for the Python
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interpreter, you might want to start Python in the DOS prompt. To make this
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work, you need to set your :envvar:`%PATH%` environment variable to include the
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directory of your Python distribution, delimited by a semicolon from other
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entries. An example variable could look like this (assuming the first two
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entries are Windows' default)::
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C:\WINDOWS\system32;C:\WINDOWS;C:\Python25
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Typing :command:`python` on your command prompt will now fire up the Python
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interpreter. Thus, you can also execute your scripts with command line options,
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see :ref:`using-on-cmdline` documentation.
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Python usually stores its library (and thereby your site-packages folder) in the
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installation directory. So, if you had installed Python to
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:file:`C:\\Python\\`, the default library would reside in
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:file:`C:\\Python\\Lib\\` and third-party modules should be stored in
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:file:`C:\\Python\\Lib\\site-packages\\`.
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This is how :data:`sys.path` is populated on Windows:
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* An empty entry is added at the start, which corresponds to the current
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* If the environment variable :envvar:`PYTHONPATH` exists, as described in
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:ref:`using-on-envvars`, its entries are added next. Note that on Windows,
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paths in this variable must be separated by semicolons, to distinguish them
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from the colon used in drive identifiers (``C:\`` etc.).
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* Additional "application paths" can be added in the registry as subkeys of
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:samp:`\\SOFTWARE\\Python\\PythonCore\\{version}\\PythonPath` under both the
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``HKEY_CURRENT_USER`` and ``HKEY_LOCAL_MACHINE`` hives. Subkeys which have
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semicolon-delimited path strings as their default value will cause each path
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to be added to :data:`sys.path`. (Note that all known installers only use
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HKLM, so HKCU is typically empty.)
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* If the environment variable :envvar:`PYTHONHOME` is set, it is assumed as
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"Python Home". Otherwise, the path of the main Python executable is used to
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locate a "landmark file" (``Lib\os.py``) to deduce the "Python Home". If a
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Python home is found, the relevant sub-directories added to :data:`sys.path`
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(``Lib``, ``plat-win``, etc) are based on that folder. Otherwise, the core
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Python path is constructed from the PythonPath stored in the registry.
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* If the Python Home cannot be located, no :envvar:`PYTHONPATH` is specified in
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the environment, and no registry entries can be found, a default path with
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relative entries is used (e.g. ``.\Lib;.\plat-win``, etc).
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The end result of all this is:
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* When running :file:`python.exe`, or any other .exe in the main Python
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directory (either an installed version, or directly from the PCbuild
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directory), the core path is deduced, and the core paths in the registry are
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ignored. Other "application paths" in the registry are always read.
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* When Python is hosted in another .exe (different directory, embedded via COM,
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etc), the "Python Home" will not be deduced, so the core path from the
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registry is used. Other "application paths" in the registry are always read.
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* If Python can't find its home and there is no registry (eg, frozen .exe, some
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very strange installation setup) you get a path with some default, but
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Python scripts (files with the extension ``.py``) will be executed by
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:program:`python.exe` by default. This executable opens a terminal, which stays
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open even if the program uses a GUI. If you do not want this to happen, use the
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extension ``.pyw`` which will cause the script to be executed by
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:program:`pythonw.exe` by default (both executables are located in the top-level
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of your Python installation directory). This suppresses the terminal window on
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You can also make all ``.py`` scripts execute with :program:`pythonw.exe`,
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setting this through the usual facilities, for example (might require
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administrative rights):
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#. Launch a command prompt.
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#. Associate the correct file group with ``.py`` scripts::
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assoc .py=Python.File
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#. Redirect all Python files to the new executable::
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ftype Python.File=C:\Path\to\pythonw.exe "%1" %*
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Even though Python aims to be portable among all platforms, there are features
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that are unique to Windows. A couple of modules, both in the standard library
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and external, and snippets exist to use these features.
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The Windows-specific standard modules are documented in
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:ref:`mswin-specific-services`.
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The `PyWin32 <https://pypi.python.org/pypi/pywin32>`_ module by Mark Hammond
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is a collection of modules for advanced Windows-specific support. This includes
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* `Component Object Model <https://www.microsoft.com/com/>`_ (COM)
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* `Microsoft Foundation Classes <https://msdn.microsoft.com/en-us/library/fe1cf721%28VS.80%29.aspx>`_ (MFC)
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`PythonWin <https://web.archive.org/web/20060524042422/
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https://www.python.org/windows/pythonwin/>`_ is a sample MFC application
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shipped with PyWin32. It is an embeddable IDE with a built-in debugger.
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`Win32 How Do I...? <http://timgolden.me.uk/python/win32_how_do_i.html>`_
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`Python and COM <http://www.boddie.org.uk/python/COM.html>`_
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by David and Paul Boddie
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`Py2exe <http://www.py2exe.org/>`_ is a :mod:`distutils` extension (see
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:ref:`extending-distutils`) which wraps Python scripts into executable Windows
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programs (:file:`{*}.exe` files). When you have done this, you can distribute
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your application without requiring your users to install Python.
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Since Python's advanced terminal handling layer, :mod:`curses`, is restricted to
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Unix-like systems, there is a library exclusive to Windows as well: Windows
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Console I/O for Python.
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`WConio <http://newcenturycomputers.net/projects/wconio.html>`_ is a wrapper for
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Turbo-C's :file:`CONIO.H`, used to create text user interfaces.
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Compiling Python on Windows
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===========================
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If you want to compile CPython yourself, first thing you should do is get the
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`source <https://www.python.org/downloads/source/>`_. You can download either the
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latest release's source or just grab a fresh `checkout
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<https://docs.python.org/devguide/setup.html#getting-the-source-code>`_.
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For Microsoft Visual C++, which is the compiler with which official Python
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releases are built, the source tree contains solutions/project files. View the
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:file:`readme.txt` in their respective directories:
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+--------------------+--------------+-----------------------+
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| Directory | MSVC version | Visual Studio version |
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+====================+==============+=======================+
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| :file:`PC/VC6/` | 6.0 | 97 |
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+--------------------+--------------+-----------------------+
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| :file:`PC/VS7.1/` | 7.1 | 2003 |
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+--------------------+--------------+-----------------------+
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| :file:`PC/VS8.0/` | 8.0 | 2005 |
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+--------------------+--------------+-----------------------+
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| :file:`PCbuild/` | 9.0 | 2008 |
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+--------------------+--------------+-----------------------+
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Note that not all of these build directories are fully supported. Read the
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release notes to see which compiler version the official releases for your
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version are built with.
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Check :file:`PC/readme.txt` for general information on the build process.
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For extension modules, consult :ref:`building-on-windows`.
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`Python + Windows + distutils + SWIG + gcc MinGW <http://sebsauvage.net/python/mingw.html>`_
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or "Creating Python extensions in C/C++ with SWIG and compiling them with
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MinGW gcc under Windows" or "Installing Python extension with distutils
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and without Microsoft Visual C++" by Sébastien Sauvage, 2003
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`MingW -- Python extensions <http://oldwiki.mingw.org/index.php/Python%20extensions>`_
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by Trent Apted et al, 2007
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`Python Programming On Win32 <http://shop.oreilly.com/product/9781565926219.do>`_
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"Help for Windows Programmers"
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by Mark Hammond and Andy Robinson, O'Reilly Media, 2000,
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`A Python for Windows Tutorial <http://www.imladris.com/Scripts/PythonForWindows.html>`_
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by Amanda Birmingham, 2004
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