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Speed up import time by deferring inspect #499

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merged 4 commits into from
Aug 20, 2024
Merged

Speed up import time by deferring inspect #499

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8e66fbc
Defer import inspect
danielhollas Aug 5, 2024
debb516
Don't use global var
danielhollas Aug 20, 2024
e99c105
Restore single-expression logic.
jaraco Aug 20, 2024
a7aaf72
Use third-person imperative voice and link to issue in comment.
jaraco Aug 20, 2024
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17 changes: 11 additions & 6 deletions importlib_metadata/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,6 @@
import zipp
import email
import types
import inspect
import pathlib
import operator
import textwrap
Expand Down Expand Up @@ -1071,6 +1070,9 @@ def _topmost(name: PackagePath) -> Optional[str]:
return top if rest else None


inspect = None
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@danielhollas danielhollas Aug 5, 2024 •
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This is a trick that is used in stdlib. I am not sure it is needed here, but since get_toplevel_name is called in a loop from _top_level_inferred perhaps it is warranted to avoid the overhead of calling import inspect repeatedly.

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I'm not a fan of global variables or the additional complexity. This change introduces enough disruption to the essential logical flow that I'm -1. Do we know how much overhead there is in repeated import inspect? My understanding (which may be incorrect) is that import inspect is essentially a dict lookup if it's already been imported. I'm guessing the overhead is acceptable. Can we try a simple deferral for now?



def _get_toplevel_name(name: PackagePath) -> str:
"""
Infer a possibly importable module name from a name presumed on
Expand All @@ -1089,11 +1091,14 @@ def _get_toplevel_name(name: PackagePath) -> str:
>>> _get_toplevel_name(PackagePath('foo.dist-info'))
'foo.dist-info'
"""
return _topmost(name) or (
# python/typeshed#10328
inspect.getmodulename(name) # type: ignore
or str(name)
)
n = _topmost(name)
if n:
return n

global inspect
if inspect is None:
import inspect
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Since we don't have a test protecting this behavior, I'd like to see a comment pointing to the issue, so a future someone doesn't refactor this optimization away.

return inspect.getmodulename(name) or str(name)


def _top_level_inferred(dist):
Expand Down
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