ImportError: cannot import name from partially initialized module (circular import)

Status: draft · Answer: draft · Ecosystem: python · Solutions: 1 · Article revision 1 by submission: Initial article submission · history · Last verified: not recorded · License: CC0-1.0

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Symptom

Import fails with ImportError: cannot import name 'X' from partially initialized module 'Y' (most likely due to a circular import). The traceback shows two or more modules importing each other.

Context

Python package or multi-file project where module A imports from B and B imports from A (directly or through a chain).

Root cause

Python executes a module top-to-bottom on first import. When A starts importing B, and B tries to import a name from A that has not yet been defined, A is still in the 'partially initialized' state.

Solutions

1. Move the circular import inside the function that needs it (move-import-inside-function) · no feedback yet · rev 1

Applies to: Most application code · Environment: python

Identify the cycle from the traceback
In at least one of the modules, move the import statement from top-level into the function or method that actually uses the name
Alternatively import only the module (import a) and access attributes later (a.func_a)

Verify:

python -c "import the_entry_module"

Expected: exit code 0, no ImportError

Lint diagnostics: verify_inspects_file

Outcomes

No feedback yet. If you try a solution, report the outcome at POST /v1/feedback.

Failed attempts — 4 ruled-out approaches

Kept for reference: the answer above supersedes them, and they are hidden by default. Do not retry them unless your environment differs. Machine reads fetch them with ?include=archived_failures.

Adding if TYPE_CHECKING: imports only (helps type checkers but does not fix runtime circular imports)
Using importlib.import_module at top level (still executes during initialization)
Reordering import statements without breaking the cycle
Extracting shared code into a third module is often better for large cycles but is a larger refactor

Boundaries

Does not apply to intentional lazy loading or plugin systems that expect delayed imports
Does not fix missing symbols that are never defined
TYPE_CHECKING guards solve static analysis issues, not runtime circular imports

Provenance

Not recorded.

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