Building Python using Microsoft Visual C++
This directory is used to build CPython for Microsoft Windows NT version
5.1 or higher (Windows XP, Windows Server 2003, or later) on 32 and 64
bit platforms. Using this directory requires an installation of
Microsoft Visual C++ 2010 (MSVC 10.0) of any edition. The specific
requirements are as follows:
Visual C++ 2010 Express Edition
Required for building 32-bit Debug and Release configuration builds.
This edition does not support "solution folders", which pcbuild.sln
uses; this will not prevent building.
Visual Studio 2010 Professional Edition
Required for building 64-bit Debug and Release configuration builds
Visual Studio 2010 Premium Edition
Required for building Release configuration builds that make use of
Profile Guided Optimization (PGO), on either platform.
The official Python releases are built with PGO using Visual Studio 2010
All you need to do to build is open the solution "pcbuild.sln" in Visual
Studio, select the desired combination of configuration and platform,
then build with "Build Solution" or the F7 keyboard shortcut. You can
also build from the command line using the "build.bat" script in this
directory. The solution is configured to build the projects in the
The solution currently supports two platforms. The Win32 platform is
used to build standard x86-compatible 32-bit binaries, output into this
directory. The x64 platform is used for building 64-bit AMD64 (aka
x86_64 or EM64T) binaries, output into the amd64 sub-directory which
will be created if it doesn't already exist. The Itanium (IA-64)
platform is no longer supported. See the "Building for AMD64" section
below for more information about 64-bit builds.
Four configuration options are supported by the solution:
Used to build Python with extra debugging capabilities, equivalent
to using ./configure --with-pydebug on UNIX. All binaries built
using this configuration have "_d" added to their name:
python35_d.dll, python_d.exe, parser_d.pyd, and so on. Both the
build and rt (run test) batch files in this directory accept a -d
option for debug builds. If you are building Python to help with
development of CPython, you will most likely use this configuration.
Used to build Python in Release configuration using PGO, which
requires Professional Edition of Visual Studio. See the "Profile
Guided Optimization" section below for more information. Build
output from each of these configurations lands in its own
sub-directory of this directory. The official Python releases are
built using these configurations.
Used to build Python as it is meant to be used in production
settings, though without PGO.
You can find build directories for older versions of Visual Studio and
Visual C++ in the PC directory. The legacy build directories are no
longer actively maintained and may not work out of the box.
Currently, the only legacy build directory is PC\VS9.0, for Visual
Studio 2008 (9.0).
Visual Studio 2010 uses version 10 of the C runtime (MSVCRT10). The
executables no longer use the "Side by Side" assemblies used in previous
versions of the compiler. This simplifies distribution of applications.
The run time libraries are available under the VC/Redist folder of your
Visual Studio distribution. For more info, see the Readme in the
The CPython project is split up into several smaller sub-projects which
are managed by the pcbuild.sln solution file. Each sub-project is
represented by a .vcxproj and a .vcxproj.filters file starting with the
name of the sub-project. These sub-projects fall into a few general
The following sub-projects represent the bare minimum required to build
a functioning CPython interpreter. If nothing else builds but these,
you'll have a very limited but usable python.exe:
.dll and .lib
kill_python.exe, a small program designed to kill any instances of
python(_d).exe that are running and live in the build output
directory; this is meant to avoid build issues due to locked files
helpers to provide necessary information to the build process
These sub-projects provide extra executables that are useful for running
CPython in different ways:
pythonw.exe, a variant of python.exe that doesn't open a Command
py.exe, the Python Launcher for Windows, see
pyw.exe, a variant of py.exe that doesn't open a Command Prompt
_testembed.exe, a small program that embeds Python for testing
purposes, used by test_capi.py
These are miscellaneous sub-projects that don't really fit the other
categories. By default, these projects do not build in Debug
_freeze_importlib.exe, used to regenerate Python\importlib.h after
changes have been made to Lib\importlib\_bootstrap.py
..\Lib\distutils\command\wininst-10.0[-amd64].exe, the base
executable used by the distutils bdist_wininst command
python3.dll, the PEP 384 Stable ABI dll
builds an example module that makes use of the PEP 384 Stable ABI,
The following sub-projects are for individual modules of the standard
library which are implemented in C; each one builds a DLL (renamed to
.pyd) of the same name as the project:
The following Python-controlled sub-projects wrap external projects.
Note that these external libraries are not necessary for a working
interpreter, but they do implement several major features. See the
"Getting External Sources" section below for additional information
about getting the source for building these libraries. The sub-projects
Python wrapper for version 1.0.6 of the libbzip2 compression library
Python wrapper for the liblzma compression library, using pre-built
binaries of XZ Utils version 5.0.5
Python wrapper for version 1.0.1h of the OpenSSL secure sockets
library, which is built by ssl.vcxproj
Building OpenSSL requires nasm.exe (the Netwide Assembler), version
2.10 or newer from
to be somewhere on your PATH. More recent versions of OpenSSL may
need a later version of NASM. If OpenSSL's self tests don't pass,
you should first try to update NASM and do a full rebuild of
The ssl sub-project expects your OpenSSL sources to have already
been configured and be ready to build. If you get your sources
from svn.python.org as suggested in the "Getting External Sources"
section below, the OpenSSL source will already be ready to go. If
you want to build a different version, you will need to run
That script will prepare your OpenSSL sources in the same way that
those available on svn.python.org have been prepared. Note that
Perl must be installed and available on your PATH to configure
OpenSSL. ActivePerl is recommended and is available from
The ssl sub-project does not have the ability to clean the OpenSSL
build; if you need to rebuild, you'll have to clean it by hand.
Wraps SQLite 220.127.116.11, which is itself built by sqlite3.vcxproj
Wraps version 8.6.1 of the Tk windowing system.
Tkinter's dependencies are built by the tcl.vcxproj and tk.vcxproj
projects. The tix.vcxproj project also builds the Tix extended
widget set for use with Tkinter.
Those three projects install their respective components in a
directory alongside the source directories called "tcltk" on
Win32 and "tcltk64" on x64. They also copy the Tcl and Tk DLLs
into the current output directory, which should ensure that Tkinter
is able to load Tcl/Tk without having to change your PATH.
The tcl, tk, and tix sub-projects do not have the ability to clean
their builds; if you need to rebuild, you'll have to clean them by
Getting External Sources
The last category of sub-projects listed above wrap external projects
Python doesn't control, and as such a little more work is required in
order to download the relevant source files for each project before they
can be built. The buildbots must ensure that all libraries are present
before building, so the easiest approach is to run either external.bat
or external-amd64.bat (depending on platform) in the ..\Tools\buildbot
directory from ..\, i.e.:
This extracts all the external sub-projects from
via Subversion (so you'll need an svn.exe on your PATH) and places them
in ..\.. (relative to this directory).
It is also possible to download sources from each project's homepage,
though you may have to change the names of some folders in order to make
things work. For instance, if you were to download a version 5.0.7 of
XZ Utils, you would need to extract the archive into ..\..\xz-5.0.5
anyway, since that is where the solution is set to look for xz. The
same is true for all other external projects.
Building for AMD64
The build process for AMD64 / x64 is very similar to standard builds,
you just have to set x64 as platform. In addition, the HOST_PYTHON
environment variable must point to a Python interpreter (at least 2.4),
to support cross-compilation from Win32. Note that Visual Studio
requires Professional Edition or better in order to build 64-bit
Profile Guided Optimization
The solution has two configurations for PGO. The PGInstrument
configuration must be built first. The PGInstrument binaries are linked
against a profiling library and contain extra debug information. The
PGUpdate configuration takes the profiling data and generates optimized
The build_pgo.bat script automates the creation of optimized binaries.
It creates the PGI files, runs the unit test suite or PyBench with the
PGI python, and finally creates the optimized files.
for more on this topic.
The solution has no configuration for static libraries. However it is
easy to build a static library instead of a DLL. You simply have to set
the "Configuration Type" to "Static Library (.lib)" and alter the
preprocessor macro "Py_ENABLE_SHARED" to "Py_NO_ENABLE_SHARED". You may
also have to change the "Runtime Library" from "Multi-threaded DLL
(/MD)" to "Multi-threaded (/MT)".
Visual Studio properties
The PCbuild solution makes heavy use of Visual Studio property files
(*.props). The properties can be viewed and altered in the Property
Manager (View -> Other Windows -> Property Manager).
The property files used are (+-- = "also imports"):
* debug (debug macro: _DEBUG)
* pginstrument (PGO)
* pgupdate (PGO)
* pyd (python extension, release build)
* pyd_d (python extension, debug build)
* pyproject (base settings for all projects, user macros like PyDllName)
* release (release macro: NDEBUG)
* sqlite3 (used only by sqlite3.vcxproj)
* tcltk (used by _tkinter, tcl, tk and tix projects)
* x64 (AMD64 / x64 platform specific settings)
The pyproject property file defines _WIN32 and x64 defines _WIN64 and
_M_X64 although the macros are set by the compiler, too. The GUI doesn't
always know about the macros and confuse the user with false
Your Own Extension DLLs
If you want to create your own extension module DLL (.pyd), there's an
example with easy-to-follow instructions in ..\PC\example\; read the
file readme.txt there first.