Python C extension: Use extension PYD or DLL?

Question

I have a Python extension written in C and I wonder if I should use the file extension DLL or PYD under Windows. (And what would I use in Linux?)

Are there any differences (besides the filename)?

I found an unofficial article. Is this the secret of pyc? Why can't I find any official article on this topic?

Answer 1

pyd files are just dll files ready for python importing.

To distinguish them from normal dlls, I recommend .pyd not .dll in windows.

Here is the official doc about this issue:

http://docs.python.org/faq/windows.html#is-a-pyd-file-the-same-as-a-dll

Answer 2

According to the Creating Your Own Project step (Step 7 of "The Cookbook Approach") of Building C and C++ Extensions on Windows

The output file should be called spam.pyd (in Release mode) or spam_d.pyd (in Debug mode). The extension .pyd was chosen to avoid confusion with a system library spam.dll to which your module could be a Python interface.

So a .pyd file is just a DLL renamed to save on confusion.

On linux however, speaking from experience it seems that you need to use the .so extension for python dlls. This is just a standard unix shared library. I can't provide a source or reason for why python on linux does not change the file extension, however I can show you how to demonstrate it. At the shell, run the following:

python -vv >>> import fakemodule 

You'll notice that the output shows:

trying /usr/lib/python2.5/site-packages/fakemodule.so