Incorrect formatting small negative floats

[bomzheg]

Bug report

Bug description:

>>> f"{-0.00000001:.2f}"
'-0.00'

expected result is 0.00

CPython versions tested on:

3.10, 3.11, 3.12

Operating systems tested on:

Linux, Windows

[Eclips4]

Hello! Thanks for the report.

In fact, you can use z format specifier which was introduced in 3.11 (b0b836b):

>>> f"{-0:z.2f}"
'0.00'

So, there's no bug.

[skirpichev]

expected result is 0.00

I'm just curious on which ground it was "expected". The C stdlib works same way, e.g.:

>>> import ctypes
>>> libc = ctypes.CDLL('libc.so.6')
>>> libc.printf(b"%.2f\n", ctypes.c_double(-0.00000001))
-0.00
6

[terryjreedy]

Unless accompanied by a reference to the Python doc, 'expected' usually means 'according to my experience, knowledge, and desire'.

@bomzheg https://discuss.python.org/c/help/7 is a better place to ask about possible bugs, as answers are more easily found there by others.