Cython notes

cython_note.md

Install

pip install cython

Build

• setuptools
  • setup.py

    from setuptools import setup
    from Cython.Build import cythonize
    
    setup(
        name='Hello world app',
        ext_modules=cythonize(
            ['hello.pyx'],
            annotate=True, # enable generation of the HTML annotation files
            compiler_directives={
                'language_level': 3, # Python3
            }
        ),
        zip_safe=False,
    )

  • build: python setup.py build_ext --inplace
  • build files(with analysis will generate HTML files): cython -a hello.pyx
• Jupyter Notebook
  • load: %load_ext Cython
  • compile: %%cython (with analysis %%cython --annotate)

Exceptions

cdef double func(double x) except? -2:
    return x ** 2 - x

• except -1: whenever returns -1, an exception will be assumed to have occurred
• except? -1: whenever returns -1, it will check with PyErr_Occurred()
• except *: always check with PyErr_Occurred() (external C++ except +)