# ImportError: cannot import name Mapping from collections after python 3.10 upgrade

TL;DR: The abstract-base-class aliases were removed from `collections` in Python 3.10 - they live in `collections.abc` now. Change the import to `from collections.abc import Mapping`. It is a one-line fix, then sweep for the other moved names so they do not bite you one at a time.

```text
ImportError: cannot import name Mapping from collections after python 3.10 upgrade
```

## Steps

1. Find every bad import: `grep -rn "from collections import" --include="*.py" .`
   Expected: a list of files importing Mapping (or Sequence, Iterable, and friends) from `collections`.
2. Fix each one: rewrite as `from collections.abc import Mapping`, keeping the rest of the import list unchanged.
   Expected: no remaining `from collections import` lines naming abstract base classes.
3. Re-run the failing command.
   Expected: imports succeed with no ImportError.
4. Run the test suite - or at least import every module - to catch the same pattern in rarely-executed code.
   Expected: no further ImportErrors from other moved names.

## Use this when

- The ImportError names Mapping, Sequence, MutableMapping, Iterable, Callable, or similar, imported from `collections`.
- The code just moved to Python 3.10 or newer.
- The same import worked on 3.9 (with a deprecation warning you may have missed).

## Not for this skill when

- The unimportable name was never in `collections` - check the spelling and the real home module.
- You are on Python 3.9 or older - the aliases still work there.
- A third-party package has the same bug - upgrade the package instead of patching your code around it.

## Variant phrasings

- collections Mapping deprecated import error python 3.10
- from collections.abc import Mapping fix
- python 3.10 abstract base classes moved

## Why it happens

The ABC aliases in `collections` were deprecated since Python 3.3 and finally removed in 3.10. Their canonical home has been `collections.abc` for a decade - the upgrade just deleted the forwarding aliases.

## Edge cases

- The same removal hits Sequence, MutableMapping, MutableSequence, Iterable, Iterator, Callable, and more - fix them all in one grep pass.
- Vendored or pinned old dependencies can carry the same import - upgrading them beats patching around them.
- If you must support old and new Pythons, a try/except fallback import (try `collections.abc`, fall back to `collections`) keeps one codebase working on both.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_D64wSfN-eXt-94X6YBGadw