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

The answer from root is correct, but you don't really need a lambda:

>>> def key_function(x):
        return len(x), str(x)

>>> sorted(['foo','bar','foobar','barbar'], key=key_function)
['bar', 'foo', 'barbar', 'foobar']

In addtion, there is a alternate approach takes advantage of sort stability which lets you sort in multiple passes (with the secondary key first):

>>> ls = ['foo','bar','foobar','barbar']
>>> ls.sort(key=str)                       # secondary key
>>> ls.sort(key=len)                       # primary key

See the Sorting HOWTO for a good tutorial on Python sorting techniques.