[Python 3.10 Issues] Deprecation

 

1) from collections import X breaks (Mapping/MutableMapping/Iterable, etc.)

 

Symptoms

 

• ImportError: cannot import name 'Mapping' from 'collections'
   

• Similar errors for MutableMapping, Iterable, Sequence, etc.

 

Why

 

The ABCs stopped being re-exported from collections in 3.10. You must import them from collections.abc. This had been warned about for years and finally flipped in 3.10.

 

Fix (drop-in)

 

 

Prevent it next time

 

• Grep your code and templates for from collections import.
   

• Add a linter rule or CI check that fails on from collections import (Mapping|MutableMapping|Iterable|...).
   

• If a dependency still imports from collections, upgrade it or patch locally.

 

2) parser module removal

 

Symptoms

 

• ModuleNotFoundError: No module named 'parser'

• Tools that relied on old LL(1) parser internals stop working.

 

Why

 

CPython switched to the PEG parser in 3.9. The legacy parser module and related C APIs were removed in 3.10.

 

Fix / Migration paths

 

• If you parsed Python code: use ast or modern libraries like LibCST / Parso.
   

• If you generated/inspected bytecode: use ast, dis, or higher-level introspection APIs.
   

• If you depended on lib2to3/pgen2 style grammars, plan a move - those won’t parse future grammar changes reliably.

 

 

Prevent it next time

 

• Avoid relying on undocumented internals; prefer ast and well-maintained parsing libs.
   

• Skim “Removed” sections of each What’s New before upgrading.

 

3) asyncio’s loop= parameter removal

 

Symptoms

 

• TypeError: ... got an unexpected keyword argument 'loop'
   

• Failing code like asyncio.Queue(loop=loop), asyncio.Lock(loop=loop), asyncio.gather(..., loop=loop).

 

 

Why

 

loop= had been deprecated; in 3.10 it’s removed from most high-level APIs. The event loop is now discovered via asyncio.get_running_loop(), or managed by asyncio.run().

 

Fix (typical patterns)

 

 

• Need the loop object? Inside a coroutine: loop = asyncio.get_running_loop().
   

• Creating tasks: prefer asyncio.create_task() inside running code.

 

Prevent it next time

 

• Keep your async style “modern”: asyncio.run, create_task, get_running_loop only when required.
   

• In libs, avoid exposing loop juggling to users.

 

4) distutils deprecation warnings

 

Symptoms

 

• Warnings like: distutils is deprecated and slated for removal in Python 3.12.

 

Why

 

PEP 632: distutils was deprecated in 3.10, fully removed in 3.12.

 

Fix (modern build backend)

 

• Move to a pyproject.toml build with Setuptools/Flit/Hatch.

  Example:
   

 

• Replace from distutils... imports with Setuptools or packaging equivalents.

 

Prevent it next time

 

• Track PyPA and PEP updates; avoid stdlib packaging APIs slated for removal.

 

5) Smaller but notable gotchas

 

• importlib migration (find_module → find_spec): Old patterns using pkgutil.find_loader/imp.find_module should move to importlib.util.find_spec.
   

• C-API/Embedding changes: Read Python 3.10 C API changes if you maintain C extensions.

 

 

Upgrade playbook

 

1. Run tests on 3.10 early (use tox/CI matrix).
    

2. Fail on deprecations: pytest -W error::DeprecationWarning
    

3. Automate fixes: replace from collections import with collections.abc, remove loop= in asyncio.
    

4. Modernize packaging with pyproject.toml.
    

5. Pin and upgrade dependencies.
    

6. Read What’s New in 3.10 before rollout.