Message 362306 - Python tracker

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Author	ammar2
Recipients	Akos Kiss, ammar2, eric.smith, serhiy.storchaka, vstinner
Date	2020-02-20.10:48:15
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<1582195695.97.0.848798276338.issue39694@roundup.psfhosted.org>
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Content
Can re-create, this is because the kwargs handling inside unicode format only performs a lookup when needed https://github.com/python/cpython/blob/c4cacc8c5eab50db8da3140353596f38a01115ca/Objects/stringlib/unicode_format.h#L393-L424 and doesn't eagerly check it like here https://github.com/python/cpython/blob/ffd9753a944916ced659b2c77aebe66a6c9fbab5/Objects/call.c#L985-L1010 This might not be worth fixing though because of the very common pattern of "{abcd}".format(locals()) This would take a pretty dramatic performance hit for a relatively uncommon edge case.

Can re-create, this is because the **kwargs handling inside unicode format only performs a lookup when needed https://github.com/python/cpython/blob/c4cacc8c5eab50db8da3140353596f38a01115ca/Objects/stringlib/unicode_format.h#L393-L424 and doesn't eagerly check it like here https://github.com/python/cpython/blob/ffd9753a944916ced659b2c77aebe66a6c9fbab5/Objects/call.c#L985-L1010

This might not be worth fixing though because of the very common pattern of 

  "{abcd}".format(**locals())

This would take a pretty dramatic performance hit for a relatively uncommon edge case.

History
Date	User	Action	Args
2020-02-20 10:48:16	ammar2	set	recipients: + ammar2, vstinner, eric.smith, serhiy.storchaka, Akos Kiss
2020-02-20 10:48:15	ammar2	set	messageid: <1582195695.97.0.848798276338.issue39694@roundup.psfhosted.org>
2020-02-20 10:48:15	ammar2	link	issue39694 messages
2020-02-20 10:48:15	ammar2	create