https://github.com/python/cpython/commit/65ed1b742985ea615d47988fda72090b177... commit: 65ed1b742985ea615d47988fda72090b177f0b45 branch: 3.13 author: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> committer: brettcannon <brett@python.org> date: 2024-07-03T21:14:42Z summary: [3.13] gh-117983: Defer import of threading for lazy module loading (GH-120233) (GH-121349) gh-117983: Defer import of threading for lazy module loading (GH-120233) As noted in gh-117983, the import importlib.util can be triggered at interpreter startup under some circumstances, so adding threading makes it a potentially obligatory load. Lazy loading is not used in the stdlib, so this removes an unnecessary load for the majority of users and slightly increases the cost of the first lazily loaded module. An obligatory threading load breaks gevent, which monkeypatches the stdlib. Although unsupported, there doesn't seem to be an offsetting benefit to breaking their use case. For reference, here are benchmarks for the current main branch: ``` ❯ hyperfine -w 8 './python -c "import importlib.util"' Benchmark 1: ./python -c "import importlib.util" Time (mean ± σ): 9.7 ms ± 0.7 ms [User: 7.7 ms, System: 1.8 ms] Range (min … max): 8.4 ms … 13.1 ms 313 runs ``` And with this patch: ``` ❯ hyperfine -w 8 './python -c "import importlib.util"' Benchmark 1: ./python -c "import importlib.util" Time (mean ± σ): 8.4 ms ± 0.7 ms [User: 6.8 ms, System: 1.4 ms] Range (min … max): 7.2 ms … 11.7 ms 352 runs ``` Compare to: ``` ❯ hyperfine -w 8 './python -c pass' Benchmark 1: ./python -c pass Time (mean ± σ): 7.6 ms ± 0.6 ms [User: 5.9 ms, System: 1.6 ms] Range (min … max): 6.7 ms … 11.3 ms 390 runs ``` This roughly halves the import time of importlib.util. (cherry picked from commit 94f50f8ee6872007d46c385f7af253497273255a) Co-authored-by: Chris Markiewicz <effigies@gmail.com> files: A Misc/NEWS.d/next/Library/2024-06-07-10-10-32.gh-issue-117983.NeMR9n.rst M Lib/importlib/util.py diff --git a/Lib/importlib/util.py b/Lib/importlib/util.py index c94a148e4c50e0..284206b62f9409 100644 --- a/Lib/importlib/util.py +++ b/Lib/importlib/util.py @@ -13,7 +13,6 @@ import _imp import sys -import threading import types @@ -257,6 +256,9 @@ def create_module(self, spec): def exec_module(self, module): """Make the module load lazily.""" + # Threading is only needed for lazy loading, and importlib.util can + # be pulled in at interpreter startup, so defer until needed. + import threading module.__spec__.loader = self.loader module.__loader__ = self.loader # Don't need to worry about deep-copying as trying to set an attribute diff --git a/Misc/NEWS.d/next/Library/2024-06-07-10-10-32.gh-issue-117983.NeMR9n.rst b/Misc/NEWS.d/next/Library/2024-06-07-10-10-32.gh-issue-117983.NeMR9n.rst new file mode 100644 index 00000000000000..cca97f50a20496 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2024-06-07-10-10-32.gh-issue-117983.NeMR9n.rst @@ -0,0 +1,2 @@ +Defer the ``threading`` import in ``importlib.util`` until lazy loading is +used.