解决因类型标注导致的循环导入报错

demo.py

# 解决因类型标注导致的循环导入报错

# file1.py
from typing import TYPE_CHECKING  # https://docs.python.org/3/library/typing.html#typing.TYPE_CHECKING

if TYPE_CHECKING:  # 关键
    from file2 import C2

class C1:
    def __init__(self, c2_self: "C2"):  # 关键，以字符串标注
        ...

# ----------------------------------------------- 

# file2.py
from typing import TYPE_CHECKING

if TYPE_CHECKING:  # 关键
    from file1 import C1
    
class C2:
    def __init__(self, c1_self: "C1"):  # 关键，以字符串标注
        ...