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GeezerVison is showing github.com — bpo-31581: Reduce the number of imports for functools by methane · Pull Request #3757 · python/cpython

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@methane

@methane methane commented Sep 26, 2017 •
edited by bedevere-bot
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Since functools and collections are very commonly used, it's worth enough to optimize import.

https://bugs.python.org/issue31581

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@methane
methane requested review from ncoghlan and rhettinger as code owners September 26, 2017 03:55
@the-knights-who-say-ni the-knights-who-say-ni added the CLA signed label Sep 26, 2017
@bedevere-bot bedevere-bot added the awaiting merge label Sep 26, 2017
@methane methane added the skip news label Sep 26, 2017
@methane

methane commented Sep 26, 2017

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I added 'skip news' tag, since #1269 don't have news too.
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ncoghlan
ncoghlan previously requested changes Sep 26, 2017
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@ncoghlan ncoghlan left a comment

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The functools.singledispatch change seems reasonable to me, since the cost of checking the import cache twice will be cheap compared to the overhead of defining a new function to apply @singledispatch to.

As per the comments on the argparse PR, this should be accompanied by a comment explaining the trade-off (i.e. there are many programs that use functools without singledispatch, so we trade-off making singledispatch marginally slower for the benefit of making start-up of such applications slightly faster)

However, I'm less sure of the appropriateness of the start-up vs runtime cost trade-off for Counter.most_common, so I'd prefer to see that change in a separate PR.

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@bedevere-bot

bedevere-bot commented Sep 26, 2017

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A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I didn't expect the Spanish Inquisition!. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.
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@bedevere-bot bedevere-bot added awaiting changes and removed awaiting merge labels Sep 26, 2017
methane added 2 commits September 26, 2017 17:19
@methane
Reduce the number of imports for functools
d648fc8
@methane
Revert collections module
f228a84
@methane
methane force-pushed the bpo31518-functools-import branch from a0082b6 to f228a84 Compare September 26, 2017 08:47
methane added 2 commits September 26, 2017 17:51
@methane
Add comment about lazy import
cac0c73
@methane
Fix TestSingleDispatch
865f333
serhiy-storchaka
serhiy-storchaka reviewed Sep 26, 2017
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Comment thread Lib/functools.py Outdated
# There are many programs that use functools without singledispatch, so we
# trade-off making singledispatch marginally slower for the benefit of
# making start-up of such applications slightly faster.
from types import MappingProxyType

@serhiy-storchaka serhiy-storchaka Sep 26, 2017

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It is slightly faster to import types and use types.MappingProxyType once than import MappingProxyType from types. The from ... import case runs a Python code from _bootstrap.py, while the former case runs just a C code if the types module already is imported.

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Comment thread Lib/test/test_functools.py Outdated
def clear(self):
self.data.clear()
_orig_wkd = functools.WeakKeyDictionary
_orig_wkd = weakref.WeakKeyDictionary

@serhiy-storchaka serhiy-storchaka Sep 26, 2017

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Use try ... finally or test.support.swap_attr() for guaranteeing that weakref.WeakKeyDictionary is restored if the following checks fail.

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methane added 2 commits September 27, 2017 18:16
@methane
Use import instead of from ... import
fd86dde
@methane
Use support.swap_attr in TestSingleDispatch
26b0b32
@methane

methane commented Sep 28, 2017

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However, I'm less sure of the appropriateness of the start-up vs runtime cost trade-off for Counter.most_common, so I'd prefer to see that change in a separate PR.

fixed.
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@methane
Add import comment at top of the module.
99eeeb9 
ref: https://bugs.python.org/issue31581#msg303366
@methane
methane dismissed ncoghlan’s stale review September 30, 2017 06:57

fixed

@methane
methane merged commit 9811e80 into python:master Sep 30, 2017
@methane
methane deleted the bpo31518-functools-import branch September 30, 2017 07:13
@Mariatta Mariatta removed the awaiting changes label Oct 4, 2017
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@serhiy-storchaka serhiy-storchaka serhiy-storchaka left review comments
@ncoghlan ncoghlan ncoghlan left review comments
@rhettinger rhettinger Awaiting requested review from rhettinger

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6 participants

@methane @bedevere-bot @ncoghlan @serhiy-storchaka @Mariatta @the-knights-who-say-ni
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