Cython embed on Windows

Question

I have read How to enable `--embed` with cythonize? and Cython --embed flag in setup.py but this method does not work on Windows. Let's say we have:

# app.py
print("hello")

# build.py
import setuptools   # allows us to avoid calling vcvarsall.bat, see https://stackoverflow.com/a/53172602/
from distutils.core import setup
from Cython.Build import cythonize
from Cython.Compiler import Options
Options.embed = "main"
setup(ext_modules=cythonize(r'app.py', build_dir="release"), script_args=['build'], options={'build': {'build_lib': 'release'}})

Running this build.py script on Python 3.8 for Windows does not produce an app.exe file like it would with the command line command:

cython app.py --embed

Instead, it produces a .pyd file.

How to use cythonize + embed from a Python script, producing a .exe, on Windows?

I take it you tried to add a `if __name__ == '__main__':` statement inside the .py file. I always just compile Cython as PYDs and haven't tried the embed option before. But since the `Options.embed = "main"` refers to something not in the .py file, it could be the issue. — Matt, Jul 18 '22 at 20:00
@Matt If I'm correct, it sadly doesn't solve the problem here. It seems here that there is a Cython bug: `Options.embed = "main"` is not used on Windows. — Basj, Jul 18 '22 at 20:02

score 1 · Accepted Answer · answered Jul 20 '22 at 20:29

Solved: in fact the problem did not come from cythonize itself, but from the fact distutils.core.setup(...) is configured to compile+link into a .pyd instead of a .exe.

Here is the solution:

from distutils._msvccompiler import MSVCCompiler    # "from distutils.msvccompiler" did not work for me!
from Cython.Compiler import Options
Options.embed = "main"
cythonize(r'src\app.py', build_dir="build")

compiler = MSVCCompiler()
compiler.compile([r"build\src\app.c"], include_dirs=["C:/Python38/include"])
compiler.link_executable([r"build\src\app.obj"], "app", libraries=["python38"], library_dirs=["C:/Python38/libs"], output_dir="release", extra_preargs=["/NOIMPLIB", "/NOEXP"])

The .exe will be in the release folder.

(Note: I also upgraded Cython to the latest version 0.29.30, it might have helped as well)

Cython embed on Windows

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