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 File > Open Workspace
dialog (not File > Open!). 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
Build > Select Active Configuration 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 Build > Build
example_d.dll in Debug mode, or Build >
Build example.dll in Release mode. This creates all
intermediate and result files in a subdirectory called either
Debug or Release, depending on which
configuration you selected in the preceding step.
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):
C>..\..\PCbuild\python_d
Adding parser accelerators ...
Done.
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
[4897 refs]
>>> example.foo()
Hello, world
[4903 refs]
>>>
Congratulations! You've successfully built your first Python
extension module.
Cretating 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 dialog).
Creating a brand new project
Use the File > New > Projects 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 Project > Settings 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 directories:
..\Include,..\PC
Then, choose the Input category in the Link tab, and enter
..\PCbuild
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
python22.lib to the list in the ``Object/library modules''
box.
Select ``Win32 Debug'' in the ``Settings for'' dropdown list, and
append python22_d.lib 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 Insert > Files
into Project 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:
PyObject_HEAD_INIT(&PyType_Type)
Change it to:
PyObject_HEAD_INIT(NULL)
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.