Longest Common Substring, Dynamic

long_substr.py

"""http://stackoverflow.com/questions/2892931/longest-common-substring-from-more-than-two-strings-python"""

def long_substr(data):
    """Finds the longest common string in any arbitrary array of strings"""
    substr = ''
    if len(data) > 1 and len(data[0]) > 0:
        for i in range(len(data[0])):
            for j in range(len(data[0])-i+1):
                if j > len(substr) and all(data[0][i:i+j] in x for x in data):
                    substr = data[0][i:i+j]
    return substr

print long_substr(['Oh, hello, my friend.',
                   'I prefer Jelly Belly beans.',
                   'When hell freezes over!'])    

longest_common_substring.py

"""From wikipedia. Not as clean as could be. 
You don't really need to create the matrix explicitly.
Only handles two strings.
But, it's a good port of how a more typical language would do it."""

def longest_common_substring(s1, s2):
  """Finds the longest common string given two strings"""
  m = [[0] * (1 + len(s2)) for i in xrange(1 + len(s1))]
  longest, x_longest = 0, 0
  for x in xrange(1, 1 + len(s1)):
      for y in xrange(1, 1 + len(s2)):
          if s1[x - 1] == s2[y - 1]:
              m[x][y] = m[x - 1][y - 1] + 1
              if m[x][y] > longest:
                  longest = m[x][y]
                  x_longest = x
          else:
              m[x][y] = 0
  return s1[x_longest - longest: x_longest]