Flatten Python lists and tuples into their individual items

flatten.py

def flatten(li):
    """Flatten lists or tuples into their individual items. If those items are
    again lists or tuples, flatten those."""

    if isinstance(li, (list, tuple)):
        for item in li:
            yield from flatten(item)
    else:
        yield li

You could make this broader/more complex by checking for instances of abstract base classes instead of (list, tuple).

Taken from this discussion on Stack Overflow: Flatten an irregular list of lists