utils.py 文件源码

def unique_everseen(iterable, key=None):
    """
    The generator to list unique elements, preserving the order. Remember all
    elements ever seen. This was taken from the itertools recipes.

    Args:
        iterable: An iterable to process.
        key: Optional function to run when checking elements (e.g., str.lower)

    Returns:
        Generator: Yields a generator object.
    """

    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