text: # Copyright (c) 2011 Google Inc. All rights reserved.
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions are
  # met:
  #
  #     * Redistributions of source code must retain the above copyright
  # notice, this list of conditions and the following disclaimer.
  #     * Redistributions in binary form must reproduce the above
  # copyright notice, this list of conditions and the following disclaimer
  # in the documentation and/or other materials provided with the
  # distribution.
  #     * Neither the name of Google Inc. nor the names of its
  # contributors may be used to endorse or promote products derived from
  # this software without specific prior written permission.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  from array import array
  
  
  def edit_distance(str1, str2):
      unsignedShort = 'h'
      distances = [array(unsignedShort, (0,) * (len(str2) + 1)) for i in range(0, len(str1) + 1)]
      # distances[0][0] = 0 since distance between str1[:0] and str2[:0] is 0
      for i in range(1, len(str1) + 1):
          distances[i][0] = i  # Distance between str1[:i] and str2[:0] is i
  
      for j in range(1, len(str2) + 1):
          distances[0][j] = j  # Distance between str1[:0] and str2[:j] is j
  
      for i in range(0, len(str1)):
          for j in range(0, len(str2)):
              diff = 0 if str1[i] == str2[j] else 1
              # Deletion, Insertion, Identical / Replacement
              distances[i + 1][j + 1] = min(distances[i + 1][j] + 1, distances[i][j + 1] + 1, distances[i][j] + diff)
      return distances[len(str1)][len(str2)]
  