Documentation of `n` in the format-specifier should reference locale-setting

[stefmolin]

Documentation

I was trying out the option of using n in a format specifier to use locale-aware thousands and decimal separators. I was surprised to see it didn't do anything on my machine, despite locale.getlocale() returning what I expected:

>>> import locale
>>> locale.getlocale()
('en_US', 'UTF-8')
>>> x = 12345
>>> f'{x:n}'
'12345'

I did some more digging and realized I needed to do locale.setlocale(locale.LC_NUMERIC, 'en_US') first, which was neither obvious nor mentioned in the documentation where it introduces the n option:

>>> import locale
>>> locale.setlocale(locale.LC_NUMERIC, 'en_US')
>>> x = 12345
>>> f'{x:n}'
'12,345'

I propose adding a mention that the locale.LC_NUMERIC must be set in this section as a helpful cross-reference.

Linked PRs

• gh-134887: Add references to locale module for locale-aware number formatting references in string module docs #134888
• [3.15] gh-134887: Add references to locale module for locale-aware number formatting references in string module docs (GH-134888) #150120
• [3.14] gh-134887: Add references to locale module for locale-aware number formatting references in string module docs (GH-134888) #150121
• [3.13] gh-134887: Add references to locale module for locale-aware number formatting references in string module docs (GH-134888) #150122