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gh-137855: Lazy importinspect module in dataclasses#144387
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| # If this is a wrapped function, unwrap it. | ||
| member=inspect.unwrap(member) | ||
| ifnotisinstance(member,type)andhasattr(member,'__wrapped__'): |
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This check was copied from the while loop ininspect.unwrap
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danielhollas commentedFeb 2, 2026
Deferring the call to $./python -m cProfile -m _colorize| head 20 5604 function calls (5484 primitive calls) in 0.007 seconds Ordered by: cumulative time ncalls tottime percall cumtime percall filename:lineno(function) 9/1 0.004 0.000 0.007 0.007 {built-in method builtins.exec} 1 0.000 0.000 0.007 0.007 <string>:1(<module>) 1 0.000 0.000 0.007 0.007 <frozen runpy>:199(run_module) 1 0.000 0.000 0.007 0.007 <frozen runpy>:65(_run_code) 1 0.000 0.000 0.007 0.007 _colorize.py:1(<module>) 7 0.000 0.000 0.006 0.001 dataclasses.py:1432(wrap) 7 0.000 0.000 0.006 0.001 dataclasses.py:986(_process_class) 7 0.000 0.000 0.004 0.001 dataclasses.py:478(add_fns_to_class) 4 0.000 0.000 0.001 0.000 inspect.py:3343(signature) 4 0.000 0.000 0.001 0.000 inspect.py:3056(from_callable) 12/4 0.000 0.000 0.001 0.000 inspect.py:2437(_signature_from_callable) 4 0.000 0.000 0.001 0.000 inspect.py:2331(_signature_from_function) 71/11 0.000 0.000 0.000 0.000 annotationlib.py:907(get_annotations) 8 0.000 0.000 0.000 0.000 dataclasses.py:541(__annotate__) 17/9 0.000 0.000 0.000 0.000 annotationlib.py:1114(_get_and_call_annotate) |
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inspectmodule is slow to import (see#117865) and is dragging down dataclasses with it.There are currently only two uses of
inspectin dataclasses, but they are a bit tricky to inline since they are on a direct code path when the@dataclassdecorator is executed.inspect.signatureis used to autogenerate class docstring (if one is not provided already)inspect.unwrapis used in a rather esoteric code path only for slotted classes, added ingh-90562: Improve zero argument support forsuper()in dataclasses whenslots=True#124692)For 1. I have used a descriptor protocol to generate the
__doc__attribute on demand (this is my first time messing with descriptors, apologies if I overlooked something).For 2. can be defferred by calling the unwrap functions only when really necessary (and hopefully this path is not common)
Benchmarks
./python -Ximporttime -c "import dataclasses"Before
After
Overall seems to be a solid 20-30% improvement.
TODO (if things done here seem acceptable):
ensure_lazy_importstest fixture