Module import mechanism

When importing a module A, all imports in this module A and other modules in __init__.py where module A is located will be imported first, and the import of module A will be completed after importing these.

Generation of circular import

During the process of importing module A, other packages import the module itself

Workaround

1. Introduce the package that causes the circular import into the function that uses it, that is, import it when the package is run
2. If this module is only used for type hint, it is only used for static detection and not used at runtime.The following methods can be used.

from __future__ import annotations # must be placed at the beginning of the filefrom typing import TYPE_CHECKINGif TYPE_CHECKING:from module x import xxx

3. Put the involved packages in a separate folder to avoid the joint import of other imports