Remove duplicates from list

remove_duplicates.py

from types import GeneratorType


def remove_duplicates(iterable, key=None):
    iterable_class = type(iterable)
    if iterable_class in [dict, set]:
        raise TypeError("You can't remove duplicates from a {}!".format(iterable_class))

    if not key:
        _key = lambda a: a
    elif not callable(key):
        _key = lambda a: a[key]
    else:
        _key = key

    s = set()
    gen = (s.add(_key(i)) or i for i in iterable if _key(i) not in s)

    if iterable_class == str:
        return ''.join(gen)
    elif iterable_class == GeneratorType:
        return list(gen)

    return iterable_class(gen)