Source Code for Module nltk.chat.util

  1  # Natural Language Toolkit: Chatbot Utilities 
  2  # 
  3  # Copyright (C) 2001-2008 NLTK Project 
  4  # Authors: Steven Bird <[email protected]> 
  5  # URL: <http://nltk.org> 
  6  # For license information, see LICENSE.TXT 
  7   
  8  # Based on an Eliza implementation by Joe Strout <[email protected]>, 
  9  # Jeff Epler <[email protected]> and Jez Higgins <[email protected]>. 
 10   
 11  import string 
 12  import re 
 13  import random 
 14   
 15  reflections = { 
 16    "am"     : "are", 
 17    "was"    : "were", 
 18    "i"      : "you", 
 19    "i'd"    : "you would", 
 20    "i've"   : "you have", 
 21    "i'll"   : "you will", 
 22    "my"     : "your", 
 23    "are"    : "am", 
 24    "you've" : "I have", 
 25    "you'll" : "I will", 
 26    "your"   : "my", 
 27    "yours"  : "mine", 
 28    "you"    : "me", 
 29    "me"     : "you" 
 30  } 
 31   
 32 -class Chat(object): 
 33 -    def __init__(self, pairs, reflections={}): 
 34          """ 
 35          Initialize the chatbot.  Pairs is a list of patterns and responses.  Each 
 36          pattern is a regular expression matching the user's statement or question, 
 37          e.g. r'I like (.*)'.  For each such pattern a list of possible responses 
 38          is given, e.g. ['Why do you like %1', 'Did you ever dislike %1'].  Material 
 39          which is matched by parenthesized sections of the patterns (e.g. .*) is mapped to 
 40          the numbered positions in the responses, e.g. %1. 
 41   
 42          @type pairs: C{list} of C{tuple} 
 43          @param pairs: The patterns and responses 
 44          @type reflections: C{dict} 
 45          @param reflections: A mapping between first and second person expressions 
 46          @rtype: C{None} 
 47          """ 
 48   
 49          self._pairs = [(re.compile(x, re.IGNORECASE),y) for (x,y) in pairs] 
 50          self._reflections = reflections 
 51   
 52      # bug: only permits single word expressions to be mapped 
 53 -    def _substitute(self, str): 
 54          """ 
 55          Substitute words in the string, according to the specified reflections, 
 56          e.g. "I'm" -> "you are" 
 57           
 58          @type str: C{string} 
 59          @param str: The string to be mapped 
 60          @rtype: C{string} 
 61          """ 
 62   
 63          words = "" 
 64          for word in string.split(string.lower(str)): 
 65              if self._reflections.has_key(word): 
 66                  word = self._reflections[word] 
 67              words += ' ' + word 
 68          return words 
 69   
 70 -    def _wildcards(self, response, match): 
 71          pos = string.find(response,'%') 
 72          while pos >= 0: 
 73              num = string.atoi(response[pos+1:pos+2]) 
 74              response = response[:pos] + \ 
 75                  self._substitute(match.group(num)) + \ 
 76                  response[pos+2:] 
 77              pos = string.find(response,'%') 
 78          return response 
 79   
 80 -    def respond(self, str): 
 81          """ 
 82          Generate a response to the user input. 
 83           
 84          @type str: C{string} 
 85          @param str: The string to be mapped 
 86          @rtype: C{string} 
 87          """ 
 88   
 89          # check each pattern 
 90          for (pattern, response) in self._pairs: 
 91              match = pattern.match(str) 
 92   
 93              # did the pattern match? 
 94              if match: 
 95                  resp = random.choice(response)    # pick a random response 
 96                  resp = self._wildcards(resp, match) # process wildcards 
 97   
 98                  # fix munged punctuation at the end 
 99                  if resp[-2:] == '?.': resp = resp[:-2] + '.' 
100                  if resp[-2:] == '??': resp = resp[:-2] + '?' 
101                  return resp 
102   
103      # Hold a conversation with a chatbot 
104 -    def converse(self, quit="quit"): 
105          input = "" 
106          while input != quit: 
107              input = quit 
108              try: input = raw_input(">") 
109              except EOFError: 
110                  print input 
111              if input: 
112                  while input[-1] in "!.": input = input[:-1] 
113                  print self.respond(input) 
114