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GeezerVison is showing github.com — gh-148871: Add CONSTANT_EMPTY_TUPLE to LOAD_COMMON_CONSTANT by eendebakpt · Pull Request #149688 · python/cpython

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@eendebakpt

@eendebakpt eendebakpt commented May 11, 2026 •
edited by bedevere-app Bot
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Add () as a new value for LOAD_COMMON_CONSTANT, following the existing pattern used for "" (CONSTANT_EMPTY_STR). The compiler now folds LOAD_CONST () into LOAD_COMMON_CONSTANT 12, dropping the entry from co_consts.

() is the most common constant left in co_consts after the existing LOAD_COMMON_CONSTANT rewrites. Frequencies in co_consts (top-level entries, recursing into nested code objects):

Constant stdlib (613,524 entries) pyperformance (9,550 entries) Immortal singleton?
() 14,270 (2.33%) 112 (1.17%) yes (Py_CONSTANT_EMPTY_TUPLE)
b"" 1,012 (0.16%) 4 (0.04%) yes (Py_CONSTANT_EMPTY_BYTES)
1.0 516 (0.08%) 14 (0.15%) no (would need new immortal float)
0.0 457 (0.07%) 13 (0.14%) no (would need new immortal float; care re: -0.0)
... 139 (0.02%) 1 (0.01%) yes (_Py_EllipsisObject)

Common sources of (): __slots__ = (), empty default-args tuples passed to MAKE_FUNCTION, __reduce__ returning (), etc.

b"" and ... are already immortal singletons, but less frequent. For reviewers: should we add these as well?

  • Issue: Extend and improve LOAD_COMMON_CONSTANT #148871

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@eendebakpt
eendebakpt requested review from FFY00, ZeroIntensity, ericsnowcurrently, iritkatriel and markshannon as code owners May 11, 2026 15:24
@python-cla-bot

python-cla-bot Bot commented May 11, 2026 •
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@bedevere-app bedevere-app Bot mentioned this pull request May 11, 2026
Extend and improve LOAD_COMMON_CONSTANT #148871
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@bedevere-app bedevere-app Bot added the awaiting review label May 11, 2026
@eendebakpt @claude
Add CONSTANT_EMPTY_TUPLE to LOAD_COMMON_CONSTANT
79cc39d 
Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>
@eendebakpt
eendebakpt force-pushed the load-common-const-empty-tuple branch from 84e6f85 to 79cc39d Compare May 11, 2026 15:28
@eendebakpt @claude
Add NEWS entry for pythongh-148871
56d633a 
Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>
@markshannon

markshannon commented May 19, 2026

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There are, inevitably, merge conflicts.
Happy to merge when they're fixed
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@eendebakpt
Merge remote-tracking branch 'origin/main' into load-common-const-emp…
369fe77 
…ty-tuple

# Conflicts:
#	Include/internal/pycore_opcode_utils.h
#	Lib/opcode.py
#	Python/pylifecycle.c
markshannon
markshannon approved these changes May 21, 2026
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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting review labels May 21, 2026
@markshannon
markshannon merged commit f2fa291 into python:main May 21, 2026
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@bedevere-app bedevere-app Bot removed the awaiting merge label May 21, 2026
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@markshannon markshannon markshannon approved these changes
@ericsnowcurrently ericsnowcurrently Awaiting requested review from ericsnowcurrently ericsnowcurrently is a code owner
@ZeroIntensity ZeroIntensity Awaiting requested review from ZeroIntensity ZeroIntensity is a code owner
@FFY00 FFY00 Awaiting requested review from FFY00 FFY00 is a code owner
@iritkatriel iritkatriel Awaiting requested review from iritkatriel iritkatriel is a code owner

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@eendebakpt @markshannon
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