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How To Build Python Extensions Without a Microsoft Compiler

These note were written by Jaco Smuts. If you have any questions about them, please e-mail Jaco directly.

Notes on how to compile Python extensions on windows without the Microsoft compiler. I assume some basic skills in Windows. Most of this is simply copied from http://sebsauvage.net/python/mingw.html.

Steps:

  1. Get and install MinGW gcc
  2. Create libpython2?.a
  3. Tweak distutils
  4. Compile/install the extension with distutils.

Get and install MinGW gcc

Get MinGW gcc from http://mingw.org (Minimalist GNU For Windows). I’ve only downloaded MinGW-3.1.0-1.exe (14.8 Mb). This will install the compiler, libraries and support utilities in your chosen directory. I can’t remember if I had to do this manually, make sure your {install dir}\bin is added to your path environment variable. To test it type gcc – version in at the command prompt to test your installation.

Create libpython2?.a

To create Python extensions, you need to link against the Python library. Unfortunately, most Python distributions are provided with Python2?.lib, a library in Microsoft Visual C++ format. GCC expects a .a file (libpython2?.a to be precise.). Here’s how to convert python2?.lib to libpython2?.a:

  1. Download pexports from http://starship.python.net/crew/kernr/mingw32/.

  2. Extract files and make sure the bin directory is in your path.

  3. Locate Python2?.dll (Found mine under C:\WINNT\system32).

  4. Run:

    pexports python2?.dll > python2?.def
    

    This will extract all symbols from python2?.dll and write them into python2?.def.

  5. Run:

    dlltool --dllname python2?.dll --def python2?.def --output-lib libpython2?.a
    

    This will create libpython2?.a (dlltool is part of MinGW utilities).

  6. Copy libpython2?.a to {your install}\python2?\libs\ (in the same directory as python22.lib). This trick should work for all Python versions, including future releases of Python. You can also use this trick to convert other libraries. (Will see about that soon)

Tweak Distutils

From memory, this was not required for my python 2.3 version, I include this for the sake of completeness.

You can compile and link your Python extensions yourself, but distutil is the preffered way (it will make all the necessary calls to the different compilers, call SWIG if necessary and your extensions will be easier to distribute). Locate build_ext.py in your Python directory (should be somewhere around C:\Python22\Lib\distutils\command\). Change the 2 following lines:

#new_sources.append(base + target_ext) # old
new_sources.append(base + '_wrap' + target_ext) # new

#swig_cmd = [swig, "-python", "-dnone", "-ISWIG"] # old
swig_cmd = [swig, "-python"] # new

Compile/install the extension with distutils

This is how I compiled the pymqi extension..

There seems to be a problem doing the install with the build in one go, so I first build then I install without building In the setup.py file I changed the include_dirs to:

C:/Program Files/IBM/WebSphere MQ/Tools/c/include

Library_dirs to:

C:/Program Files/IBM/WebSphere MQ/Tools/Lib

(note the forward slashes) Then I run:

setup.py build -cmingw32 client

or:

setup.py build -cmingw32 server

next the install:

setup.py install --skip-build

(note I’m doing the install and the build separately)


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