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AST optimizer: Change a list into tuple in iterations and containment tests #77106
Description
| BPO | 32925 |
|---|---|
| Nosy | @brettcannon, @ncoghlan, @scoder, @benjaminp, @serhiy-storchaka, @1st1 |
| PRs |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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GitHub fields:
assignee = None
closed_at = <Date 2018-03-11.08:57:09.458>
created_at = <Date 2018-02-23.21:44:18.191>
labels = ['interpreter-core', '3.8', 'performance']
title = 'AST optimizer: Change a list into tuple in iterations and containment tests'
updated_at = <Date 2018-03-11.08:57:09.457>
user = 'https://github.com/serhiy-storchaka'bugs.python.org fields:
activity = <Date 2018-03-11.08:57:09.457>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2018-03-11.08:57:09.458>
closer = 'serhiy.storchaka'
components = ['Interpreter Core']
creation = <Date 2018-02-23.21:44:18.191>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 32925
keywords = ['patch']
message_count = 4.0
messages = ['312670', '312703', '312828', '313588']
nosy_count = 6.0
nosy_names = ['brett.cannon', 'ncoghlan', 'scoder', 'benjamin.peterson', 'serhiy.storchaka', 'yselivanov']
pr_nums = ['5842']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'performance'
url = 'https://bugs.python.org/issue32925'
versions = ['Python 3.8']
Activity
serhiy-storchaka commentedon Feb 23, 2018
Currently a list of constants is replaced with constant tuple in
x in [1, 2]andfor x in [1, 2]. The resulted AST is the same as forx in (1, 2)andfor x in (1, 2).The proposed simple PR extends this optimization to lists containing non-constants.
x in [a, b]will be changed intox in (a, b)andfor x in [a, b]will be changed intofor x in (a, b). Since creating a tuple is faster than creating a list the latter form is a tiny bit faster../python -m timeit -s 'a, b = 1, 2' -- '1 in [a, b]'
5000000 loops, best of 5: 58.9 nsec per loop
scoder commentedon Feb 24, 2018
An obvious optimisation, if you ask me. PR looks good to me superficially, but I don't know the AST code well.
serhiy-storchaka commentedon Feb 25, 2018
The direct inspiration of this optimization was your note that similar optimization was implemented in Python.
serhiy-storchaka commentedon Mar 11, 2018
New changeset 3f7e9aa by Serhiy Storchaka in branch 'master':
bpo-32925: Optimized iterating and containing test for literal lists (GH-5842)
3f7e9aa