Cython compiler directive的language_level未生效，编译报错求助

Let's work through resolving this compilation error step by step:

1. Fix the Obvious Command Typo #

First, I notice you're running cythonize -i world_dep.pyx but your code lives in temp.pyx—that's likely a copy-paste mistake. Make sure you target the correct file:

cythonize -i temp.pyx

2. Force Python 3 Syntax via Command Line #

If the file-level directive isn't being picked up, bypass it by specifying the language level directly in the cythonize command:

cythonize -i -3 temp.pyx

The -3 flag tells Cython to enforce Python 3 syntax rules, which will properly recognize the sep parameter in your print() call.

3. Update Your Cython Version #

Older versions of Cython had inconsistent support for the language_level=3 directive. Check your current version first:

cython --version

If you're on a version older than 0.29, upgrade to the latest stable release:

pip install --upgrade cython

Newer versions handle the language_level directive much more reliably.

4. Use a setup.py for Explicit Configuration #

For more control, define the compiler directive in a setup.py file instead of relying on the file-level comment. Create this file in the same directory as temp.pyx:

from setuptools import setup
from Cython.Build import cythonize

setup(
    ext_modules=cythonize(
        "temp.pyx",
        compiler_directives={"language_level": "3"}
    )
)

Then compile with:

python setup.py build_ext --inplace

This method ensures the language level is explicitly set during the build process, eliminating ambiguity.

Why This Happens #

The error (Expected '...' at the sep parameter) is a classic Python 2 syntax issue—Python 2's print statement doesn't support keyword arguments like sep. This means Cython was still parsing your code as Python 2, despite your language_level=3 directive. Common causes include outdated Cython versions, conflicting global configurations, or typos in your command/file path.

内容的提问来源于stack exchange，提问作者Saim Raza