Python "cannot import name 'Mapping' from collections" in CI

The abstract base classes (Mapping, Sequence, Iterable, ...) were importable from collections until 3.9 with a deprecation; 3.10 removed the alias entirely. Code or an old dependency that imports them from collections fails.

What this error means

On a Python 3.10+ runner an import fails with "ImportError: cannot import name 'Mapping' from 'collections'," often from a transitive dependency, not your own code.

python

Traceback (most recent call last):
  File ".../oldlib/utils.py", line 3, in <module>
    from collections import Mapping
ImportError: cannot import name 'Mapping' from 'collections'

Common causes

ABCs imported from collections on 3.10+

They now live in collections.abc; the legacy alias in collections was dropped in 3.10.

An unmaintained dependency uses the old path

A transitive package never updated its imports and breaks on the newer interpreter.

How to fix it

Import from collections.abc

Change your own imports to from collections.abc import Mapping.
Re-run on the 3.10+ runner.

Python

from collections.abc import Mapping, Sequence, Iterable

Upgrade or pin the offending dependency

When the bad import is in a dependency, upgrade to a version that supports 3.10+, or pin the runner Python below 3.10 if you cannot.

Terminal

pip install --upgrade the-old-lib   # to a 3.10+ compatible release

How to prevent it

Always import ABCs from collections.abc.
Keep dependencies current with your runner Python version.
Run the suite against the target Python major/minor before merging.