Compile main Python program using Cython

Question

I have a Python2.6 program that can load Python modules compiled to .so files using Cython. I used Cython to compile the .py modules to .so files and everything works fine.

This is the setup.py file I use with Cython:

from distutils.core import setup
from distutils.extension import Extension
from Cython.Distutils import build_ext

ext_modules = [
    Extension("ldap", ["ldap.pyx"]),
    Extension("checker", ["checker.pyx"]),
    Extension("finder", ["finder.pyx"]),
    Extension("utils", ["utils.pyx"]),
]

setup(
  name = 'bchecker',
  cmdclass = {'build_ext': build_ext},
  ext_modules = ext_modules
)

So I know I can compile Python modules using Cython (I guess Cython creates 'C' files from my Python files and then compiles them), but can I compile my main Python program to something I can execute on a Linux platform? If so, a Cython command line example would be appreciated. Thanks.

Answer 1

Contrary to what Adam Matan and others assert, you can in fact create a single executable binary file using Cython, from a pure Python (.py) file.

Yes, Cython is intended to be used as stated - as a way of simplifying writing C/C++ extension modules for the CPython python runtime.

But, as nudzo alludes to in this comment, you can use the --embed switch at the command line prompt.

Here is an extremely simple example. I am peforming this from a Debian Sid workstation, using python3 and cython3..

Make sure you have python-dev or python3-dev packages installed beforehand.

1) Create a very simple Python program called hello.py

$ cat hello.py

print("Hello World!")

2) Use Cython to compile your python program into C...

cython3 --embed -o hello.c hello.py

3) Use GCC to compile hello.c into an executable file called hello...

gcc -Os -I /usr/include/python3.3m -o hello hello.c -lpython3.3m -lpthread -lm -lutil -ldl

4) You end up with a file called hello ...

$ file hello

hello: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, BuildID[sha1]=006f45195a26f1949c6ed051df9cbd4433e1ac23, not stripped

$ ldd hello
linux-vdso.so.1 (0x00007fff273fe000)
libpython3.3m.so.1.0 => /usr/lib/x86_64-linux-gnu/libpython3.3m.so.1.0 (0x00007fc61dc2c000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fc61da0f000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fc61d70b000)
libutil.so.1 => /lib/x86_64-linux-gnu/libutil.so.1 (0x00007fc61d508000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fc61d304000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fc61cf5a000)
librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007fc61cd52000)
libexpat.so.1 => /lib/x86_64-linux-gnu/libexpat.so.1 (0x00007fc61cb28000)
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007fc61c90f000)
/lib64/ld-linux-x86-64.so.2 (0x00007fc61e280000)

In this case, the executable is dynamically linked to Python 3.3 on my Debian system.

5) run hello...

$ ./hello

Hello World!

As you can see, using this method you can basically use Cython to convert your pure Python applications into executable, compiled object code.

I am using this method for vastly more complex applications - for example, a full blown Python/PySide/Qt application.

For different versions of Python, you tailor the gcc -I and -l switches to suit.

You can then package the executable as a distribution (.deb, etc.) file, without having to package the Python/PySide/Qt files - the advantage being that your application should still be able to run even after a distribution update to the same versions of Python, etc. on that distribution.