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Python implicit boolean conversion in logical operations bypasses try/except on 3.14.0rc1 #137288

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#137310
Closed
Python implicit boolean conversion in logical operations bypasses try/except on 3.14.0rc1#137288
#137310
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iritkatriel
Labels
3.14bugs and security fixes3.15bugs and security fixesinterpreter-core(Objects, Python, Grammar, and Parser dirs)release-blockertype-bugAn unexpected behavior, bug, or error

Description

@justinjfu
justinjfu
opened on Jul 31, 2025

Bug report

Bug description:

Throwing an exception during an implicit cast to a boolean as part of a logical operation (or, and) bypasses surrounding try/except statements.

The following example works on Python 3.12.3 but fails on Python 3.14.0rc1:

Example:

class Foo:
  def __bool__(self):
    raise NotImplementedError()

a = Foo()
b = Foo()

# Works
try:
  c = bool(a)
except:
  print("passed c = bool(a)")

# Fails
try:
  c = a or b
except:
  print("passed c = a or b")

Output on Python 3.12.3 (expected behavior):

passed c = bool(a)
passed c = a or b

Output on Python 3.14.0rc1:

passed c = bool(a)
Traceback (most recent call last):
  File "/Users/justinfu/code/test_bool.py", line 15, in <module>
    c = a or b
        ^^^^^^
  File "/Users/justinfu/code/test_bool.py", line 3, in __bool__
    raise NotImplementedError()
NotImplementedError

CPython versions tested on:

3.14

Operating systems tested on:

macOS

Linked PRs

Activity

  1. justinjfu
    added
    type-bugAn unexpected behavior, bug, or error
    on Jul 31, 2025

  2. ethanfurman commented on Jul 31, 2025

    @ethanfurman
    ethanfurman
    on Jul 31, 2025
    Member

    Confirmed on LinuxMint.

  3. brianschubert commented on Jul 31, 2025

    @brianschubert
    brianschubert
    on Jul 31, 2025
    Contributor

    Bisects to 78aeb38 (#124394), cc @iritkatriel

  4. brianschubert
    added
    interpreter-core(Objects, Python, Grammar, and Parser dirs)
    3.14bugs and security fixes
    3.15bugs and security fixes
    on Jul 31, 2025
  5. JelleZijlstra
    added
    release-blocker
    on Aug 1, 2025
  6. ezio-melotti
    added this to Release and Deferred blockers 🚫on Aug 1, 2025
  7. github-project-automation
    moved this to Todo in Release and Deferred blockers 🚫on Aug 1, 2025
  8. iritkatriel
    self-assigned this
    on Aug 1, 2025
  9. iritkatriel
    added a commit that references this issue on Aug 1, 2025

    pythongh-137288: Fix bug where boolean expressions are not associated…

    71b151d

  10. iritkatriel commented on Aug 1, 2025

    @iritkatriel
    iritkatriel
    on Aug 1, 2025
    Member

    Thank you @justinjfu for reporting and @brianschubert for bisecting. This is a nice little bug.

    Fix in #137310

  11. iritkatriel
    added a commit that references this issue on Aug 1, 2025

    Merge branch 'main' into pythongh-137288

    58dfd02

  12. justinjfu commented on Aug 1, 2025

    @justinjfu
    justinjfu
    on Aug 1, 2025
    Author

    Thank you for the quick fix!

  13. iritkatriel
    added a commit that references this issue on Aug 3, 2025

    Merge branch 'main' into pythongh-137288

    c9ae7ef

  14. 7 remaining items

  15. hroncok
    added 7 commits that reference this issue on Aug 12, 2025

    00468: pythongh-137288: Fix bug where boolean expressions are not ass…

    64aae21

    00468: pythongh-137288: Fix bug where boolean expressions are not ass…

    8c018e1

    pythongh-137288: Fix Python version in magic number comment

    f344256

    00468: pythongh-137288: Fix bug where boolean expressions are not ass…

    7df7306

    00468: pythongh-137288: Fix bug where boolean expressions are not ass…

    84d6330

    00468: pythongh-137288: Fix bug where boolean expressions are not ass…

    dfac92a

    00468: pythongh-137288: Fix bug where boolean expressions are not ass…

    7e91859
  16. encukou
    added 2 commits that reference this issue on Aug 12, 2025

    gh-137288: Update 3.14 magic numbers (GH-137665)

    715647a

    [3.14] pythongh-137288: Update 3.14 magic numbers (pythonGH-137665)

    72a639d
  17. hugovk
    added a commit that references this issue on Aug 12, 2025

    [3.14] gh-137288: Update version in magic number log (GH-137665) (#13…

    946b226
  18. maurycy
    added a commit that references this issue on Aug 12, 2025

    Merge branch 'main' into csv-sniffer-counter-set

    11c891d
  19. Agent-Hellboy
    added 2 commits that reference this issue on Aug 19, 2025

    pythongh-137288: Fix bug where boolean expressions are not associated…

    21afcc3

    pythongh-137288: Update 3.14 magic numbers (pythonGH-137665)

    8625362
  20. kumaraditya303
    added 2 commits that reference this issue on Sep 9, 2025

    [3.14] pythongh-137288: Fix bug where boolean expressions are not ass…

    f3084ea

    [3.14] pythongh-137288: Update version in magic number log (pythonGH-…

    49d5ed0
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3.14bugs and security fixes3.15bugs and security fixesinterpreter-core(Objects, Python, Grammar, and Parser dirs)release-blockertype-bugAn unexpected behavior, bug, or error

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