Software1 hOctober 22, 2026, 21:12

Python 3.15 lazy imports cut CLI startup from 164 ms to 28 ms

Python 3.15.0 shipped on October 9, 2026, with 5,643 commits from 1,012 contributors and a delayed third release candidate to fix lazy imports. A test CLI importing 11 stdlib modules started 5.8x faster (164.1 to 28.4 ms), but import errors now surface at first use instead of startup.

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Lazy imports: 164.1 ms to 28.4 ms on an 11-module CLI
ModuleNotFoundError now raises at first touch, not at startup
frozendict is a Mapping, not a dict: isinstance(fd, dict) is False
sentinel('X') is sentinel('X') returns False; identity is not name-keyed

#Python

Python 3.15 adds explicit lazy imports with the lazy keyword

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Python 3.15 released with JIT, lazy imports, and frozendict

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Python 3.15: test shows lazy import defers the delay, not removes it

Software

Python 3.15 lazy imports cut CLI startup from 164 ms to 28 ms

Python 3.15 adds explicit lazy imports with the lazy keyword

Python 3.15 released with JIT, lazy imports, and frozendict

Python 3.15: test shows lazy import defers the delay, not removes it

Python 3.15 speeds up Base32 135x but slows Base16 by 22%