Why are arbitrary target expressions allowed in for-loops?

Question

I accidentally wrote some code like this:

foo = [42]
k = {\'c\': \'d\'}

for k[\'z\'] in foo:  # Huh??
    print k

But to my surprise, this

Answer 1

Is there any situation in which this is actually useful?

Indeed. Ever wanted to get rid of itertools.combinations?

def combinations (pool, repeat):        
    def combinations_recurse (acc, pool, index = 0):
        if index < len(acc):
            for acc[index] in pool:
                yield from combinations_recurse(acc, pool, index + 1)
        else:
            yield acc

    yield from combinations_recurse([pool[0]] * repeat, pool)

for comb in combinations([0, 1], 3):
    print(comb)