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GeezerVison is showing github.com — Incorrect overflows for complex powers when base is infinite · Issue #156693 · python/cpython

Incorrect overflows for complex powers when base is infinite #156693

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Incorrect overflows for complex powers when base is infinite#156693
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interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Description

@skirpichev
skirpichev
opened on Aug 31, 2026
Issue body actions

Bug report

Bug description:

Consider this, for example:

Python 3.16.0a0 (heads/main:ee68f5f46a1, Aug 12 2026, 11:19:39) [GCC 14.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> complex('inf+0j')**1
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    complex('inf+0j')**1
    ~~~~~~~~~~~~~~~~~^^~
OverflowError: complex exponentiation

c.f. the real case:

>>> float('inf')**1
inf

See also http://stackoverflow.com/q/18243270/270986

The generic algorithm returns a correct answer (match GNU MPC, for example), but sets errno incorrectly:

>>> import _testcapi
>>> _testcapi._py_c_pow(complex('inf'), 1)
((inf+nanj), 34)
>>> from gmpy2 import mpc
>>> mpc('inf')**1
mpc('inf+nanj')

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

  • gh-156693: correct complex powers with infinite bases #156694

Activity

  1. skirpichev
    self-assigned this
    on Aug 31, 2026
  2. skirpichev
    added
    type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error
    interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)
    on Aug 31, 2026
  3. skirpichev
    removed their assignment
    on Aug 31, 2026

  4. serhiy-storchaka commented on Sep 3, 2026

    @serhiy-storchaka
    serhiy-storchaka
    on Sep 3, 2026
    Member
    More actions

    complex('inf+0j')**1 was fixed by #124243. Are there other examples?

  5. skirpichev commented on Sep 3, 2026

    @skirpichev
    skirpichev
    on Sep 3, 2026
    MemberAuthor
    More actions

    I think no, my fix was based on #124243.

  6. skirpichev
    closed this as completedon Sep 3, 2026
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