4.1 A Cookbook Approach
There are two approaches to building extension modules on Windows, just as there are on Unix: use the distutils package to control the build process, or do
things manually. The distutils approach works well for most extensions; documentation on using
distutils to build and package
extension modules is available in Distributing Python Modules. This section describes the manual approach to
building Python extensions written in C or C++.
To build extensions using these instructions, you need to have a copy of the Python sources
of the same version as your installed Python. You will need Microsoft Visual C++ ``Developer
Studio''; project files are supplied for VC++ version 6, but you can use older versions of
VC++. The example files described here are distributed with the Python sources in the PC\ example_nt\ directory.
- Copy the example files
The example_nt directory is a subdirectory of the PC directory, in order to keep all the PC-specific files under the
same directory in the source distribution. However, the example_nt
directory can't actually be used from this location. You first need to copy or move it up
one level, so that example_nt is a sibling of the PC and Include directories. Do all your work
from within this new location.
- Open the project
From VC++, use the dialog (not
!). Navigate to and select the file example.dsw, in the copy of the example_nt
directory you made above. Click Open.
- Build the example DLL
In order to check that everything is set up right, try building:
- Select a configuration. This step is optional. Choose
and select either ``example - Win32 Release''
or ``example - Win32 Debug.'' If you skip this step, VC++ will use the Debug
configuration by default.
- Build the DLL. Choose Debug or Release, depending
on which configuration you selected in the preceding step.
in Debug mode, or in
Release mode. This creates all intermediate and result files in a subdirectory called
- Testing the debug-mode DLL
Once the Debug build has succeeded, bring up a DOS box, and change to the example_nt\Debug directory. You should now be able to repeat the
following session (
C> is the DOS prompt,
>>> is the
Python prompt; note that build information and various debug output from Python may not
match this screen dump exactly):
Adding parser accelerators ...
Python 2.2 (#28, Dec 19 2001, 23:26:37) [MSC 32 bit (Intel)] on win32
Type "copyright", "credits" or "license" for more information.
>>> import example
Congratulations! You've successfully built your first Python extension module.
- Creating your own project
Choose a name and create a directory for it. Copy your C sources into it. Note that the
module source file name does not necessarily have to match the module name, but the name
of the initialization function should match the module name -- you can only import a
module spam if its initialization function is called initspam(), and it should call Py_InitModule()
with the string
"spam" as its first argument (use the minimal example.c in this directory as a guide). By convention, it lives in a
file called spam.c or spammodule.c.
The output file should be called spam.dll or spam.pyd
(the latter is supported to avoid confusion with a system library spam.dll
to which your module could be a Python interface) in Release mode, or spam_d.dll
or spam_d.pyd in Debug mode.
Now your options are:
- Copy example.dsw and example.dsp,
rename them to spam.*, and edit them by hand, or
- Create a brand new project; instructions are below.
In either case, copy example_nt\example.def to spam\spam.def, and edit the new spam.def so
its second line contains the string `
initspam'. If you created a new project
yourself, add the file spam.def to the project now. (This is an
annoying little file with only two lines. An alternative approach is to forget about the .def file, and add the option /export:initspam
somewhere to the Link settings, by manually editing the setting in Project Options
- Creating a brand new project
Use the dialog to create a
new Project Workspace. Select ``Win32 Dynamic-Link Library,'' enter the name ("spam"), and make sure the Location is set to the spam
directory you have created (which should be a direct subdirectory of the Python build
tree, a sibling of Include and PC).
Select Win32 as the platform (in my version, this is the only choice). Make sure the
Create new workspace radio button is selected. Click OK.
Now open the dialog. You only
need to change a few settings. Make sure All Configurations is selected from the Settings
for: dropdown list. Select the C/C++ tab. Choose the Preprocessor category in the popup
menu at the top. Type the following text in the entry box labeled Addditional include
Then, choose the Input category in the Link tab, and enter
in the text box labelled ``Additional library path.''
Now you need to add some mode-specific settings:
Select ``Win32 Release'' in the ``Settings for'' dropdown list. Click the Link tab,
choose the Input Category, and append
pythonXY.lib to the list in the
``Object/library modules'' box.
Select ``Win32 Debug'' in the ``Settings for'' dropdown list, and append
to the list in the ``Object/library modules'' box. Then click the C/C++ tab, select ``Code
Generation'' from the Category dropdown list, and select ``Debug Multithreaded DLL'' from
the ``Use run-time library'' dropdown list.
Select ``Win32 Release'' again from the ``Settings for'' dropdown list. Select
``Multithreaded DLL'' from the ``Use run-time library:'' dropdown list.
You should now create the file spam.def as instructed in the
previous section. Then chose the dialog. Set the pattern to
*.* and select both spam.c and spam.def and click OK. (Inserting
them one by one is fine too.)
If your module creates a new type, you may have trouble with this line:
Change it to:
and add the following to the module initialization function:
MyObject_Type.ob_type = &PyType_Type;
Refer to section 3 of the Python FAQ for details
on why you must do this.