Source code for

# Natural Language Toolkit: Chatbot Utilities
# Copyright (C) 2001-2018 NLTK Project
# Authors: Steven Bird <>
# URL: <>
# For license information, see LICENSE.TXT

# Based on an Eliza implementation by Joe Strout <>,
# Jeff Epler <> and Jez Higgins <>.
from __future__ import print_function

import re
import random

from six.moves import input

reflections = {
  "i am"       : "you are",
  "i was"      : "you were",
  "i"          : "you",
  "i'm"        : "you are",
  "i'd"        : "you would",
  "i've"       : "you have",
  "i'll"       : "you will",
  "my"         : "your",
  "you are"    : "I am",
  "you were"   : "I was",
  "you've"     : "I have",
  "you'll"     : "I will",
  "your"       : "my",
  "yours"      : "mine",
  "you"        : "me",
  "me"         : "you"

[docs]class Chat(object): def __init__(self, pairs, reflections={}): """ Initialize the chatbot. Pairs is a list of patterns and responses. Each pattern is a regular expression matching the user's statement or question, e.g. r'I like (.*)'. For each such pattern a list of possible responses is given, e.g. ['Why do you like %1', 'Did you ever dislike %1']. Material which is matched by parenthesized sections of the patterns (e.g. .*) is mapped to the numbered positions in the responses, e.g. %1. :type pairs: list of tuple :param pairs: The patterns and responses :type reflections: dict :param reflections: A mapping between first and second person expressions :rtype: None """ self._pairs = [(re.compile(x, re.IGNORECASE),y) for (x,y) in pairs] self._reflections = reflections self._regex = self._compile_reflections() def _compile_reflections(self): sorted_refl = sorted(self._reflections.keys(), key=len, reverse=True) return re.compile(r"\b({0})\b".format("|".join(map(re.escape, sorted_refl))), re.IGNORECASE) def _substitute(self, str): """ Substitute words in the string, according to the specified reflections, e.g. "I'm" -> "you are" :type str: str :param str: The string to be mapped :rtype: str """ return self._regex.sub(lambda mo: self._reflections[mo.string[mo.start():mo.end()]], str.lower()) def _wildcards(self, response, match): pos = response.find('%') while pos >= 0: num = int(response[pos+1:pos+2]) response = response[:pos] + \ self._substitute( + \ response[pos+2:] pos = response.find('%') return response
[docs] def respond(self, str): """ Generate a response to the user input. :type str: str :param str: The string to be mapped :rtype: str """ # check each pattern for (pattern, response) in self._pairs: match = pattern.match(str) # did the pattern match? if match: resp = random.choice(response) # pick a random response resp = self._wildcards(resp, match) # process wildcards # fix munged punctuation at the end if resp[-2:] == '?.': resp = resp[:-2] + '.' if resp[-2:] == '??': resp = resp[:-2] + '?' return resp
# Hold a conversation with a chatbot
[docs] def converse(self, quit="quit"): user_input = "" while user_input != quit: user_input = quit try: user_input = input(">") except EOFError: print(user_input) if user_input: while user_input[-1] in "!.": user_input = user_input[:-1] print(self.respond(user_input))