eliza.py

   1
   2 # coding: utf-8
   3 import yaml
   4 import collections
   5 import random
   6
   7 Match = collections.namedtuple('Match', 'text, rule, bindings')
   8
   9 pronoun_swaps = {
  10     'i': 'you',
  11     'me': 'you',
  12     'my': 'your',
  13     'mine': 'yours',
  14     'am': 'are'
  15 }
  16
  17 def read_rules(rules_file):
  18     with open(rules_file) as f:
  19         rules = [{'pattern': r['pattern'].split(),
  20                  'responses': [t.split() for t in r['responses']]}
  21             for r in yaml.load(f)]
  22     return rules
  23
  24 def is_var(word):
  25     return word[0] == '?'
  26
  27
  28 def splits(item):
  29     return [(item[:i], item[i:]) for i in range(len(item)+1)]
  30
  31 def match(text, rule):
  32     return all_matches([Match(text, rule, {})])
  33
  34 def all_matches(matches):
  35     successes = []
  36     while matches:
  37         # print(matches, successes)
  38         current = matches[0]
  39         new_matches = []
  40         if successful_match(current):
  41             successes += [current.bindings]
  42         elif current.rule:
  43             new_matches = match_item(current.text, current.rule, current.bindings)
  44         matches = matches[1:] + new_matches
  45     return successes
  46
  47 def successful_match(match):
  48     return match.text == [] and match.rule == []
  49
  50 def match_item(text, rule, bindings):
  51     r0 = rule[0]
  52     if is_var(r0):
  53         if r0 in bindings:
  54             # already seen this variable
  55             if text[:len(bindings[r0])] == bindings[r0]:
  56                 return [Match(text[(len(bindings[r0])):], rule[1:], bindings)]
  57             else:
  58                 return []
  59         else:
  60             # not seen this variable yet
  61             matches = []
  62             for pre, suf in splits(text):
  63                 new_bindings = bindings.copy()
  64                 new_bindings[r0] = pre
  65                 matches += [Match(suf, rule[1:], new_bindings)]
  66             return matches
  67     elif text and text[0] == r0:
  68         return [Match(text[1:], rule[1:], bindings)]
  69     else:
  70         return []
  71
  72 def candidate_rules(rules, comment):
  73     return [(rule, bindings)
  74             for rule in rules
  75             for bindings in match(comment, rule['pattern'])]
  76
  77
  78 def fill(response, bindings):
  79     filled_response = []
  80     for w in response:
  81         if is_var(w):
  82             if w in bindings:
  83                 filled_response += bindings[w]
  84             else:
  85                 filled_response += ['MISSING']
  86         else:
  87             filled_response += [w]
  88     return filled_response
  89
  90
  91 def pronoun_person_swap(bindings):
  92     def swapped(words):
  93         sw = []
  94         for w in words:
  95             if w in pronoun_swaps:
  96                 sw += [pronoun_swaps[w]]
  97             else:
  98                 sw += [w]
  99         return sw
 100
 101     return {var: swapped(bindings[var]) for var in bindings}
 102
 103 def respond(rule, bindings):
 104     return fill(random.choice(rule['responses']), bindings)
 105
 106
 107 def eliza_loop(rules):
 108     print("Hello. I'm Eliza. What seems to be the problem?")
 109     while True:
 110         c = input("> ")
 111         if c.strip() in 'quit halt exit stop'.split(): break
 112         comment = c.split()
 113         rule, bindings = candidate_rules(rules, comment)[0]
 114         swapped_bindings = pronoun_person_swap(bindings)
 115         print(' '.join(respond(rule, swapped_bindings)))
 116
 117
 118 all_rules = read_rules('rules.yaml')
 119 eliza_loop(all_rules)
 120
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