decimal.py 文件源码

def _group_lengths(grouping):
    """Convert a localeconv-style grouping into a (possibly infinite)
    iterable of integers representing group lengths.

    """
    # The result from localeconv()['grouping'], and the input to this
    # function, should be a list of integers in one of the
    # following three forms:
    #
    #   (1) an empty list, or
    #   (2) nonempty list of positive integers + [0]
    #   (3) list of positive integers + [locale.CHAR_MAX], or

    from itertools import chain, repeat
    if not grouping:
        return []
    elif grouping[-1] == 0 and len(grouping) >= 2:
        return chain(grouping[:-1], repeat(grouping[-2]))
    elif grouping[-1] == _locale.CHAR_MAX:
        return grouping[:-1]
    else:
        raise ValueError('unrecognised format for grouping')