How to specify 2 keys in python sorted(list)?

Question

How do I sort a list of strings by key=len first then by key=str? I\'ve tried the following but it\'s not giving me the desired sort:

Answer 1

Another form that works without a lambda:

>>> [t[1] for t in sorted((len(s),s) for s in ls)]
['bar', 'foo', 'barbar', 'foobar']