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format(Fraction(1, 3), '.016f') raises ValueError

skirpichev

Bug report

Bug description:

c.f.

>>> format(float(Fraction(1, 3)), '.016f')
'0.3333333333333333'

Looking on docs, I think that float formatting better conforms to the specification.

Similar issue is valid for the width:

>>> format(float(Fraction(1, 3)), '0030.016f')
'0000000000000.3333333333333333'
>>> format(Fraction(1, 3), '0030.016f')
Traceback (most recent call last):
  File "<python-input-3>", line 1, in <module>
    format(Fraction(1, 3), '0030.016f')
    ~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.13/fractions.py", line 577, in __format__
    raise ValueError(
    ...<2 lines>...
    )
ValueError: Invalid format specifier '0030.016f' for object of type 'Fraction'

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

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