How to call C functions from Linux C executable and vice-versa

[Manomugdha Biswas]

Hi,
I have a Linux C binary (executable, not .so file). i can update (add new
files/folders if it is required) but after compilation i will get a binary
executable file.
I want to access/call few functions of this executable from python. for
this i want to use cython interface (most probably cython is the best
option!). Any other possible options are also acceptable.  the
example/documentation of cython i have seen till now, they talk about
calling c functions from c library (.so file).

can you please point me to a documentation/source code which talks about
how to call c functions from c-executable?

Regards,
Mano