Which answer is correct?

Use `for k, v in d.items():`. The `.items()` method yields (key, value) tuples.

— pythonista

Use `for k in d: v = d[k]`. Loop over keys and look up each value.

— key_first

Use `for i, (k, v) in enumerate(d.items()):` if you also need the index.

— enumerate_fan

Use `for k, v in d.iteritems():`. This is the memory-efficient way.

— py2_veteran