Can you compile a .py file with cython instead of a pyx file?

Question

I have a file foo.py, and it contains a very slow function that takes 8 minutes to compute. However, when I change the file to foo.pyx and compile it with cython with no other changes, it takes 5 minutes to compute.

My question is: if I run cython foo.py instead of cython foo.pyx and then run gcc -shared -pthread -fPIC -fwrapv -O2 -Wall -fno-strict-aliasing -I/usr/include/python2.7 -o foo.so foo.c

When I run import foo, will python import the .py file or the compiled .so file? Does the pyx really need to be there, and is there a way to force it to take the .so over the .py if it exists?

The reason for this is that I cannot change the name of foo.py without breaking code on other people's machines, but I'd really like it to be faster for my tests cases. It would be great if I could just compile it locally without worrying about breaking code elsewhere.

(I'm testing this as we speak, but its taking awhile)

Answer 1

I just tried it on Windows with some Cython code I have been working with recently. The compiled module takes precedence. This was also confirmed in both of the following questions:

What is the precedence of python compiled files in imports?

Python shared object module naming convention