How do I find the longest string in Python?

Question

Something like max(len(s1), len(s2)) will only return the maximum length. But if I actually want to find out which string is longer, and perhaps save it to another string, how is that done? max(s1,s2) seems to return the string with the larger value, but not necessarily the longest.

Note: this has to be done without lists or arrays.

Answer 1

max takes a key function which causes max to take the max key(val) for each val, yet still return the val, to wit:

>>> max("foobar", "angstalot")
'foobar'
>>> max("foobar", "angstalot", key=len)
'angstalot'

Answer 2

Just a simple conditional expression based on the length of each string is all that is needed:

longest = s1 if len(s1) > len(s2) else s2