Bug report

Bug description:

I noticed this via Hypothesis' pretty-printer for lambda functions, and tracked the divergence through the inspect module to linecache:

import linecache

def test():
    print(linecache.cache["<string>"])  # expected to raise KeyError
    assert False

If I run this snippet with python3.13 -Wignore -m pytest repro.py, or any older Python version, you'll get the expected KeyError. But if I append -n2 to the command, it prints (44, None, ['import sys;exec(eval(sys.stdin.readline()))\n'], '<string>')!

(python3.13 -m pip install pytest pytest-xdist will get the dependencies for this)

That's the popen bootstrap line from execnet, which handles running code across multiple processes for pytest-xdist. At this point I've found linecache.cache.pop("<string>", None) to be an acceptable workaround, and since I don't have any particular knowledge of either the CPython or execnet code that's as far as I investigated.

CPython versions tested on:

3.8, 3.9, 3.10, 3.11, 3.12, 3.13

Operating systems tested on:

Linux

Linked PRs

• gh-117174: Add a new route in linecache to fetch interactive source code #117500
• gh-112730: Respect tests that require environment variables with no-colorize fixes #118288
• [3.13] gh-117174: Add a new route in linecache to fetch interactive source code (GH-117500) #131060
• gh-117174: Adapt test_multiple_statements_fail_early now that we have always source #131065
• gh-117174: Fix reference leak and gdb tests #131095
• [3.13] gh-117174: Fix reference leak and gdb tests (GH-131095) #131120
• gh-117174: Skip test_gdb if Python is built with LTO #131143
• gh-117174: Adapt test_multiple_statements_fail_early to new REPL behavior (follow-up gh-131065) #131836
• [3.13] gh-117174: Adapt test_multiple_statements_fail_early to new REPL behavior (follow-up gh-131065) (GH-131836) #131841
• [3.13] gh-117174: Adapt test_multiple_statements_fail_early now that we have always source (GH-131065) #131850