Determine prefix from a set of (similar) strings

Question

I have a set of strings, e.g.

my_prefix_what_ever
my_prefix_what_so_ever
my_prefix_doesnt_matter

I simply want to find the longest common p

Answer 1

Here's my solution:

a = ["my_prefix_what_ever", "my_prefix_what_so_ever", "my_prefix_doesnt_matter"]

prefix_len = len(a[0])
for x in a[1 : ]:
    prefix_len = min(prefix_len, len(x))
    while not x.startswith(a[0][ : prefix_len]):
        prefix_len -= 1

prefix = a[0][ : prefix_len]