What does the Most likely due to a circular import error mean in Python?

What does the "Most likely due to a circular import" error mean in Python?

This error indicates that your Python code has a circular dependency—when two or more modules depend on each other directly or indirectly through import statements. This results in an import loop that Python cannot resolve during the execution of the program.

What is a circular import?

A circular import occurs when:

  • Module A imports Module B, and
  • Module B imports Module A, either directly or through other modules.

This creates a cycle where Python tries to load both modules simultaneously, but neither can complete because each is waiting for the other to finish importing.

Example of circular import

  1. # file: a.py
from b import func_b

def func_a():
    print("Function A")

# file: b.py
from a import func_a

def func_b():
    print("Function B")

Running either file results in an import error because of the circular reference.

How to fix it?

  • Restructure imports: Move import statements inside functions or methods where they are used.
  • Use a separate module: Place shared logic in a third module that both original modules import.
  • Redesign module responsibilities: Simplify dependencies to avoid cyclical imports.

What if...

ScenarioResolution
You’re unsure which file is causing the loopTrace the import tree manually or use Python tools like trace or importlib.util for debugging.
You need functions from both modulesUse lazy importing (inside functions) or create a shared utility module to hold common logic.
You're working with a large codebaseConsider refactoring into a package structure with clearly defined responsibilities to minimize tight coupling.
To quickly detect circular imports in large codebases, try running your script with verbose import logs or use tools like pylint, which often catch structural issues in module imports.

Last updated: 26 Jun 2025