def reportCSV(t):
    ret = ''
    for ev in t:
        for p in t[ev]:
            for w in t[ev][p]:
                ret += ','.join((ev, p, w, t[ev][p][w])) + '\n'
    return ret

What is a more pythonic way to do this, e.g. using itertools or the like?

In this case I'm just writing it out to a CSV file. t is a dict t[ev] is a dict t[ev][p] is a dict t[ev][p][w] is a float

I'm not sure how I'd use itertools.product in this case.