ExceptionGroup repr is misleading if original exception sequence is mutated

Bug report

Bug description:

The exception listing in repr(exc_grp) diverges from exc_grp.exceptions when the initial sequence of exceptions passed to the constructor has been mutated.

Expected behavior: The exceptions listed in repr(exc_grp) match exc_grp.exceptions, which is immutable.

Reproducer:

exceptions = list[Exception]()
exceptions.append(ValueError())
exc_grp = ExceptionGroup("", exceptions)
print(f"{exc_grp.exceptions=!r}")
print(f"{exc_grp=!r}")
print()
exceptions.clear()
print(f"{exc_grp.exceptions=!r}")
print(f"{exc_grp=!r}")

Output:

exc_grp.exceptions=(ValueError(),)
exc_grp=ExceptionGroup('', [ValueError()])

exc_grp.exceptions=(ValueError(),)
exc_grp=ExceptionGroup('', [])

Expected output:

exc_grp.exceptions=(ValueError(),)
exc_grp=ExceptionGroup('', [ValueError()])

exc_grp.exceptions=(ValueError(),)
exc_grp=ExceptionGroup('', [ValueError()])

CPython versions tested on:

3.11, 3.12, 3.13, 3.14

Operating systems tested on:

Linux

Linked PRs

I noticed that PyPy behaves the way I expected here; they use self.exceptions in BaseExceptionGroup.__repr__ instead of self.args[1]:

https://github.com/pypy/pypy/blob/release-pypy3.11-v7.3.20/pypy/module/exceptions/app_group.py#L92-L93

On CPython, it looks like BaseExceptionGroup.__repr__ resolves to BaseException.__repr__, so the repr ends up using self.args[1] instead of self.exceptions.

I skimmed the PEP and didn't see anything that indicated that either repr implementation is in violation of the PEP.

I skimmed the PEP and didn't see anything that indicated that either repr implementation is in violation of the PEP.

The PEP does reference the repr() of ExceptionGroups but not explicitly specify anything:

>>> try:
...     raise ExceptionGroup("problem", [BlockingIOError()])
... except* OSError as e:   # Would catch the error
...     print(repr(e))
... except* BlockingIOError: # Would never run
...     print('never')
...
ExceptionGroup('problem', [BlockingIOError()])

But I agree that mutating an argument which is only used to create an immutable tuple shouldn't change the repr.

This may be a part of more complex problem. See #137889.

gh-141732: Fix `ExceptionGroup` repr changing when original exception…

pythongh-141732: Fix `ExceptionGroup` repr changing when original exc…

[3.13] gh-141732: Fix ExceptionGroup repr changing when original exce…

This has been merged in main and 3.13 but cannot be merged for 3.14 because of failing CI: #142388.

Please can you check the backport?

This has been merged in main and 3.13 but cannot be merged for 3.14 because of failing CI: #142388.

Please can you check the backport?

Yes, will do!
Opened #144445

python3Packages.exceptiongroup: fix build on staging

python3Packages.exceptiongroup: fix build after cpython repr changes

[3.14] gh-141732: Fix ExceptionGroup repr changing when original exce…

Navigation Menu

Repository navigation

`ExceptionGroup` repr is misleading if original exception sequence is mutated #141732

Bug report

Bug description:

CPython versions tested on:

Operating systems tested on:

Linked PRs

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

ExceptionGroup repr is misleading if original exception sequence is mutated #141732

Description

Bug report

Bug description:

CPython versions tested on:

Operating systems tested on:

Linked PRs

Activity

gschaffner commented on Nov 19, 2025

dr-carlos commented on Nov 19, 2025

serhiy-storchaka commented on Nov 19, 2025

hugovk commented on Feb 3, 2026

dr-carlos commented on Feb 3, 2026

Metadata

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Issue actions

`ExceptionGroup` repr is misleading if original exception sequence is mutated #141732