PEP563 DEMO

gistfile1.txt

# 简单测试，只有一个文件A.py ,B.py不存在

import typing

if typing.TYPE_CHECKING:
    import B

class A:

    def func(self , input:B.Bird):
        return None
        
======================
报错提示
Traceback (most recent call last):
  File "C:\Users\USER\Documents\test.py", line 6, in <module>
    class A:
  File "C:\Users\USER\Documents\test.py", line 8, in A
    def func(self , input:B.Bird):
NameError: name 'B' is not defined