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gh-103000: Optimise dataclasses.asdict for the common case (#104364)

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Co-authored-by: David Ellis <ducksual@gmail.com>
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Alex Waygood 2023-05-10 22:43:51 +01:00 • committed by GitHub
parent e464ec9f4c
commit 7b8d7f56b6
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2 changed files with 14 additions and 5 deletions
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17
Lib/dataclasses.py
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@ -1324,11 +1324,18 @@ def _asdict_inner(obj, dict_factory):
if type(obj) in _ATOMIC_TYPES: if type(obj) in _ATOMIC_TYPES:
return obj return obj
elif _is_dataclass_instance(obj): elif _is_dataclass_instance(obj):
result = [] # fast path for the common case
for f in fields(obj): if dict_factory is dict:
value = _asdict_inner(getattr(obj, f.name), dict_factory) return {
result.append((f.name, value)) f.name: _asdict_inner(getattr(obj, f.name), dict)
return dict_factory(result) for f in fields(obj)
}
else:
result = []
for f in fields(obj):
value = _asdict_inner(getattr(obj, f.name), dict_factory)
result.append((f.name, value))
return dict_factory(result)
elif isinstance(obj, tuple) and hasattr(obj, '_fields'): elif isinstance(obj, tuple) and hasattr(obj, '_fields'):
# obj is a namedtuple. Recurse into it, but the returned # obj is a namedtuple. Recurse into it, but the returned
# object is another namedtuple of the same type. This is # object is another namedtuple of the same type. This is

2
Misc/NEWS.d/next/Library/2023-05-10-19-33-36.gh-issue-103000.j0KSfD.rst Normal file
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@ -0,0 +1,2 @@
Improve performance of :func:`dataclasses.asdict` for the common case where
*dict_factory* is ``dict``. Patch by David C Ellis.