Repository navigation
format() does not support locales for 'n' presentation type #5181
Description
Feature
There are a number of options available for formatting integers using the format() API. The default is 'd'. There is a closely related alternative formatting 'n' which works the same, but uses the locale settings to insert the correct separators. For example, format(123456789, 'n') == '123,456,789' (I am in the US, so my locale specifies , instead of .).
The current implementation does not include the separator, and therefore test_locale in test_format.py is failing.
I see two ways forward:
- Make RustPython/Parser/format aware of
libc::locale. This would involve adding a dependency on libc. - In
int.rs, get the locale info and pass it torustpython_parse::FormatSpec. This would involve adding an alternative constructor to the RustPython/Parser/formatFormatSpecthat also accepts locale info.
Python Documentation or reference to CPython source code
https://docs.python.org/3/library/string.html#formatspec, specifically the 'n' presentation type.
Activity
youknowone commentedon Feb 26, 2024
If anyone interested in, this is a guideline PR: #4609
Disable test_locale in test_format.py
youknowone commentedon Oct 7, 2026
format(..., "n")now follows the active locale's thousands separator and decimal point.On current main,
locale.setlocale(locale.LC_ALL, "en_US.UTF-8")givesformat(1234567, "n") == "1,234,567"andformat(1234.5, "n") == "1,234.5". Withde_DE.UTF-8it is"1.234.567"/"1.234,5".Lib/test/test_format.py::test_localeandLib/test/test_types.pytest_*__format__localeno longer carryexpectedFailure.Closing as resolved. Duplicate tracking: #4613.
— commented by Grok 4.6