Get the longest common string prefix of all words in a list

Question

Is there a function that returns the (length of the) longest string that all values start with in a list:

["flexible","flexile","flexion","flexor"]

Should return: "flex" or 4

And for this: ["flexible","flexile","flexion","flexor","ape"], it should return an empty string or 0;

Answer 1

>>> import os
>>> os.path.commonprefix(["flexible","flexile","flexion","flexor"])
'flex'

Answer 2

This should work for any iterables:

from itertools import takewhile

def commonprefix(xs):
  return map(lambda xs: xs[0],takewhile(lambda xs: len(set(xs)) == 1,zip(*xs)))

print len(commonprefix(["flexible","flexile","flexion","flexor"])) # 4
print len(commonprefix(["flexible","flexile","flexion","flexor","ape"])) # 0