msvc.py 文件源码

def _unique_everseen(self, iterable, key=None):
        """
        List unique elements, preserving order.
        Remember all elements ever seen.

        _unique_everseen('AAAABBBCCDAABBB') --> A B C D

        _unique_everseen('ABBCcAD', str.lower) --> A B C D
        """
        seen = set()
        seen_add = seen.add
        if key is None:
            for element in filterfalse(seen.__contains__, iterable):
                seen_add(element)
                yield element
        else:
            for element in iterable:
                k = key(element)
                if k not in seen:
                    seen_add(k)
                    yield element