循环导入：在Python Imports的领域中，了解Python

中的行为，遇到模块试图彼此导入的模块可能导致令人困惑的情况的情况。本文深入研究了Python中相互和循环（环状）导入的复杂性，解释了它们的复杂性并提供了真实的例子来说明其行为。

Complications with Circular Imports

However, issues arise when using the from ... import statement within circular imports. Consider the following scenario: module A imports a symbol from module B, which in turn imports a symbol from module A. This circular dependency creates a situation where each module requires the other to be fully loaded before it can complete its own import.

Fatal Circular Imports

Unfortunately, this type of dependency can result in an ImportError or attributeError异常。 The underlying cause is that the interpreter attempts to recursively import the same module, leading to a stack overflow.

Nonfatal Circular Imports

Despite the aforementioned issues, there exist scenarios where circular imports can coexist harmoniously, as demonstrated in the examples outlined in the original question. These exceptions typically involve combinations of top-level imports, relative imports, and importing specific attributes rather than entire modules.

Conclusion

While circular imports in Python can be inherently problematic, understanding their nuances and employing the appropriate import strategies can help developers navigate these intricate situations effectively.通过遵守这些准则，可以利用循环导入来实现所需的功能，而不会遇到任何陷阱。