Python从3.5版本开始支持type hints

# type_hint.py
def foo(a: str) -> str:
    print(a)

def bar(b) -> str:
    print(b)
    return 0

但并不会强制进行检查，也就是说类型不一致并没有什么发生

但是使用cython编译后，一切就会不一样

# setup.py
from distutils.core import setup

from Cython.Build import cythonize

setup(ext_modules=cythonize('./type_hint.py', compiler_directives={'always_allow_keywords': True}))

>>> python3 setup.py build_ext --inplace

再对编译后的.so文件进行调用

>>> import type_hint
>>> type_hint.foo(123)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-2-34d9c4e717cc> in <module>
----> 1 type_hint.foo(123)

TypeError: Argument 'a' has incorrect type (expected str, got int)

>>> import type_hint
>>> type_hint.bar('a')

a
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-4-e8fb7c0cdcb3> in <module>
----> 1 type_hint.bar('a')

~/Git/test/cython_test/type_hint.cpython-38-darwin.so in type_hint.bar()

TypeError: Expected str, got int

如果参数类型或返回类型与声明的不一致则会报错

注意：并不是所有的类型都会进行类型检查

参考：https://github.com/cython/cython/issues/3130#issue-489331603