"% -4d" format specifier produces centered output instead of left-aligned in Python 3.13.2

[11python11]

Bug report

Bug description:

m = 12
print("|% -4d|" % m)

Actual output: | 12 |
Expected output: |12 |

CPython versions tested on:

3.13

Operating systems tested on:

Windows

[picnixz]

AFAIK, this is the expected behavior. Adding a space after % and before -4d means that the sign should be retained for negative values but a space must be used for positive values (see https://docs.python.org/3/library/string.html#format-specification-mini-language). This can be observed as follows:

>>> print("|%+-4d|" % 12)
|+12 |
>>> print("|% -4d|" % 12)
| 12 |
>>> print("|% -4d|" % -12)
|-12 |

Use %-4d for regular left-alignment:

>>> print("|%-4d|" % 12)
|12  |
>>> print("|%-4d|" % -12)
|-12 |

[skirpichev]

Adding a space after % and before -4d means that the sign should be retained for negative values but a space must be used for positive values (see https://docs.python.org/3/library/string.html#format-specification-mini-language).

Quoted link is about new-style formatting. In particular, alignment controlled here by "<", "=" or ">" chars. While in C printf you control alignment with "-", as does old-style formatting.

Though, it looks like mentioned by OP behavior is specified:

(a space) A blank should be left before a positive number (or empty string) produced by a signed conversion.

A sign character ('+' or '-') will precede the conversion (overrides a “space” flag).

I also think it's consistent with the C, see e.g. https://en.wikipedia.org/wiki/Printf#Flags_field