example how map works(python3)

mymap.py

class mymap:

    def __init__(self, func, seq):
        self.func = func
        self.seq = iter(seq)

    def __iter__(self):
        return self

    def __next__(self):
        return self.func(next(self.seq))


def mymap2(func, seq):
    for e in seq:
        yield func(e)


if __name__ == '__main__':
    for i in mymap(lambda x: x*2, range(10)):
        print(i)

    for i in mymap2(lambda x: x*2, range(10)):
        print(i)