(digits, spec, min_width=1)
return sep.join(reversed(groups))
Insert thousands separators into a digit string.

    spec is a dictionary whose keys should include 'thousands_sep' and
    'grouping'; typically it's the result of parsing the format
    specifier using _parse_format_specifier.

    The min_width keyword argument gives the minimum length of the
    result, which will be padded on the left with zeros if necessary.

    If necessary, the zero padding adds an extra '0' on the left to
    avoid a leading thousands separator.  For example, inserting
    commas every three digits in '123456', with min_width=8, gives
    '0,123,456', even though that has length 9.
Insert thousands separators into a digit string.
Insert thousands separators into a digit string .
def _insert_thousands_sep(digits, spec, min_width=1):
    """Insert thousands separators into a digit string.

    spec is a dictionary whose keys should include 'thousands_sep' and
    'grouping'; typically it's the result of parsing the format
    specifier using _parse_format_specifier.

    The min_width keyword argument gives the minimum length of the
    result, which will be padded on the left with zeros if necessary.

    If necessary, the zero padding adds an extra '0' on the left to
    avoid a leading thousands separator.  For example, inserting
    commas every three digits in '123456', with min_width=8, gives
    '0,123,456', even though that has length 9.

    """

    sep = spec['thousands_sep']
    grouping = spec['grouping']

    groups = []
    for l in _group_lengths(grouping):
        if l <= 0:
            raise ValueError("group length should be positive")
        # max(..., 1) forces at least 1 digit to the left of a separator
        l = min(max(len(digits), min_width, 1), l)
        groups.append('0'*(l - len(digits)) + digits[-l:])
        digits = digits[:-l]
        min_width -= l
        if not digits and min_width <= 0:
            break
        min_width -= len(sep)
    else:
        l = max(len(digits), min_width, 1)
        groups.append('0'*(l - len(digits)) + digits[-l:])
    return sep.join(reversed(groups))
def _insert_thousands_sep ( digits , spec , min_width = 1 ) : sep = spec [ 'thousands_sep' ] grouping = spec [ 'grouping' ] groups = [ ] for l in _group_lengths ( grouping ) : if l <= 0 : raise ValueError ( "group length should be positive" ) # max(..., 1) forces at least 1 digit to the left of a separator l = min ( max ( len ( digits ) , min_width , 1 ) , l ) groups . append ( '0' * ( l - len ( digits ) ) + digits [ - l : ] ) digits = digits [ : - l ] min_width -= l if not digits and min_width <= 0 : break min_width -= len ( sep ) else : l = max ( len ( digits ) , min_width , 1 ) groups . append ( '0' * ( l - len ( digits ) ) + digits [ - l : ] ) return sep . join ( reversed ( groups ) )