python type_error ai_generated true

TypeError: can't set attributes of built-in/extension type 'datetime.datetime'

ID: python/pytest-freezegun-datetime-conflict

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80%Fix Rate
82%Confidence
0Evidence
2024-08-30First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.5.x active — — —

Root Cause

freezegun tried to patch datetime.datetime but a C-extension module (e.g. pandas, psycopg2) imported datetime earlier and holds a C-level reference that cannot be monkeypatched.

generic

中文

freezegun 尝试 patch datetime.datetime，但某个 C 扩展模块（如 pandas、psycopg2）更早导入了 datetime 并持有 C 层引用，无法被 monkeypatch。

Workarounds

  1. 90% success 
    from unittest.mock import patch
import mypkg.service

@patch('mypkg.service.datetime')
def test_now(mock_dt):
    mock_dt.utcnow.return_value = datetime(2024, 1, 1)
    ...
  2. 95% success 
    # service takes a clock=datetime.utcnow parameter
def test_now():
    svc = Service(clock=lambda: datetime(2024, 1, 1))
    assert svc.today() == date(2024, 1, 1)

Dead Ends

Common approaches that don't work:

  1. 70% fail

    Import order in tests does not control the order inside application code imported at collection time.

  2. 80% fail

    Fails for the same reason: the C extension holds a direct reference to the built-in type.