Integer presentation type in f-strings does not return expected format

Question

I'm using python 3.8 in a Docker container. This is my docker file.

# Python image
FROM python:3.8.2-buster

# Install locales
RUN apt-get update
RUN apt-get install -y locales
RUN sed -i -e 's/# it_IT.UTF-8 UTF-8/it_IT.UTF-8 UTF-8/' /etc/locale.gen && locale-gen

#etc...

I wanna format numbers according to the Italian format (ie, . as a thousands separator). Fortunately, the format-specification-mini-language says:

The ' , ' option signals the use of a comma for a thousands separator. For a locale aware separator, use the ' n ' integer presentation type instead.

I run this code inside such a container:

>>> import locale
>>> locale.setlocale(locale.LC_ALL, "it_IT.UTF-8")
>>> a = 10000000
>>> f'a is equal to {a:,}'
'a is equal to 10,000,000' # ok!
>>> f'a is equal to {a:n}'
'a is equal to 10000000'   # What!? I expected 'a is equal to 10.000.000' instead

but the last line behaves unexpectedly.

Where am I wrong? Is that a problem with my locale definition or with my usage of numbers formatting harnessing n ?

Answer 1

Try this:

import locale
locale.setlocale(locale.LC_ALL, '') 
a = 1000000    
print(f'{a:n}')  # => 1,000,000