Python: Function to flatten generator containing another generator

The easiest way is a recursive flattening function. Assuming you want to descend into every iterable except for strings, you could do this:

def flatten(it):
    for x in it:
        if (isinstance(x, collections.Iterable) and
            not isinstance(x, str)):
            for y in flatten(x):
                yield y
        else:
            yield x

Starting from Python 3.3, you can also write

def flatten(it):
    for x in it:
        if (isinstance(x, collections.Iterable) and
            not isinstance(x, str)):
            yield from flatten(x)
        else:
            yield x