An advanced (kind of) generator example.

flatten.py

def flatten(iterable):
    try:
        if isinstance(iterable, (str, bytes)):  # are recursively iterable
            raise TypeError  # could've just as well been yield iterable, then else is needed
        for item in iterable:
            yield from flatten(item)
            ## alternative (py2):
            # for nested in flatten(item):
            #    yield nested
    except TypeError:
        yield iterable