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Title: bpo-43574: Dont overallocate list literals by chadnetzer · Pull Request #24954 · python/cpython · GitHub

Open Graph Title: bpo-43574: Dont overallocate list literals by chadnetzer · Pull Request #24954 · python/cpython

X Title: bpo-43574: Dont overallocate list literals by chadnetzer · Pull Request #24954 · python/cpython

Description: Before v3.9, list literals weren't over-allocated, but this behavior regressed starting with v3.9: Switched to initializing list literals w/ LIST_EXTEND https://bugs.python.org/issue39320 #17984 Commit where over-allocation of list literals first appeared https://bugs.python.org/issue38328 #17114 6dd9b64 This changes to the original behavior of not over-allocating lists for list literals, by not over-allocating any 0-length list that is extended. Technically this is a change in behavior, as lists that are initialized to length 0, and then immediately extended, will not be over-allocated on that initial extension. This change in behavior is likely innocuous, and possibly desirable, whereas the long-standing Python behavior of not using over-allocation for list literals is almost certainly desired. Adds a test_overallocation test for lists to find regressions (assuming the regression doesn't alter the behavior of both the list-literal and list-initialization from a known length). https://bugs.python.org/issue43574

Open Graph Description: Before v3.9, list literals weren't over-allocated, but this behavior regressed starting with v3.9: Switched to initializing list literals w/ LIST_EXTEND https://bugs.python.org/issue39320 #1798...

X Description: Before v3.9, list literals weren't over-allocated, but this behavior regressed starting with v3.9: Switched to initializing list literals w/ LIST_EXTEND https://bugs.python.org/issue39320 #...

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4dbee9a Add testcase for bpo-43574 list overallocaton chadnetzer Mar 21, 2021 https://github.com/python/cpython/pull/24954/commits/4dbee9ad373de2948503d8e053c337f792286ef4
5b31470 Don't overallocate when extending an empty list chadnetzer Mar 21, 2021 https://github.com/python/cpython/pull/24954/commits/5b31470b03dcabd9f687022ed724348ccc01fb7b
172f2c0 Skip overallocation calc when not overallocating chadnetzer Mar 21, 2021 https://github.com/python/cpython/pull/24954/commits/172f2c0a4014805890ec7cbd16ea3625a569e249
d76ae2a Fix list_extend() init list changes to PEP-7 form chadnetzer Mar 22, 2021 https://github.com/python/cpython/pull/24954/commits/d76ae2a9adb9892514e804a47b77cd5738ff5195
7aad246 bpo-43574: Add NEWS chadnetzer Mar 22, 2021 https://github.com/python/cpython/pull/24954/commits/7aad246f17772e19d115a1dcd8f670dfa92fb22d
7c20c6c Add more list overallocation regression tests chadnetzer Mar 22, 2021 https://github.com/python/cpython/pull/24954/commits/7c20c6cc15873cbbc7f94c06727ce1f85c27b855
7be3ae8 Put common-case first in logical-or list_resize() chadnetzer Mar 22, 2021 https://github.com/python/cpython/pull/24954/commits/7be3ae871e2e435fbe67c372c3dfaeca8cfa0927
7436223 Adjust NEWS entry language based on PR feedback chadnetzer Mar 23, 2021 https://github.com/python/cpython/pull/24954/commits/7436223a71b2ed46fff050d956d5effa5acbd549
657d51f Allow empty list append/insert to overallocate chadnetzer Mar 24, 2021 https://github.com/python/cpython/pull/24954/commits/657d51fcb25d7653fff91c044fde3452b2bce056
4336cc6 Update test_overallocation of empty list append() chadnetzer Mar 26, 2021 https://github.com/python/cpython/pull/24954/commits/4336cc6060188b1af9976dd785696b53b865031e
19d4374 Add direct test of list-literal non-overallocation chadnetzer Apr 5, 2021 https://github.com/python/cpython/pull/24954/commits/19d43741f7cf16a1bf6e9a9094e469836a3d5c4d
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