pal_finder.py

# Ask user for text file to inspect
filename = raw_input('Enter name of text file to inspect: ')
# If the file is legit
try:
  # Grab file
  f = open(filename)
  # Read file, make all lowercase
  file_string = f.read().lower()
  # Remove all non word characters
  import re
  string = re.sub(r'\W+', '', file_string)
  # Record list of longest palendromes
  pal_list = []
  # Length of longest palendrome
  pal_len = 0
  # For each character in string, search substrings of length MAX_LENGTH and check if palendromic
  MAX_LENGTH = 50
  for m, l in enumerate(string):
    for n in range(m+2, m+MAX_LENGTH):
      substr = string[m:n+1]
      if len(substr) > 1:
        substr_rev = substr[::-1]
        if substr == substr_rev:
          print "Found \"%s\" beginning at character %s" % (substr, str(m))
          if len(substr) == pal_len:
            pal_list.append((m, substr))
          elif len(substr) > pal_len:
            pal_len = len(substr)
            pal_list = [(m, substr)]
  # List longest palindromes
  print "\n---\nLongest palendromes found:"
  for tup in pal_list:
    print "Found \"%s\" beginning at character %s" % (tup[1], str(tup[0]))

except IOError as e:
   print "Couldn't open file: %s" % e