Source Code for Module prest.cmbn

 1  #!/usr/bin/env python3 
 2  # -*- coding: utf-8 -*- 
 3   
 4  """Combiner classes to merge results from several predictors.""" 
 5   
 6  from __future__ import absolute_import, unicode_literals 
 7  import abc 
 8  import prdct 
 9   
10   
11 -class Combiner(object): 
12      """Base class for all combiners. 
13   
14      G{classtree Combiner} 
15      """ 
16   
17      __metaclass__ = abc.ABCMeta 
18   
19 -    def __init__(self): 
20          """Combiner creator.""" 
21          self.name = "Combiner dosen't set any name" 
22   
23 -    def filter(self, prediction): 
24          """Sort the tokens according to their probabilities. 
25   
26          The duplicate tokens are merged to a single token (their probabilities 
27          are summed). 
28   
29          @param prediction: 
30              It is a list of Suggestion instances. 
31          @type prediction: L{prdct.Prediction} 
32   
33          @return: 
34              The sorted Prediction instance. 
35          @rtype: Prediction 
36          """ 
37          seen_tokens = set() 
38          result = prdct.Prediction() 
39          for i, suggestion in enumerate(prediction): 
40              token = suggestion.word 
41              if token not in seen_tokens: 
42                  for j in range(i + 1, len(prediction)): 
43                      if token == prediction[j].word: 
44                          suggestion.probability += prediction[j].probability 
45                          if suggestion.probability > prdct.MAX_PROBABILITY: 
46                              suggestion.probability = prdct.MAX_PROBABILITY 
47                          elif suggestion.probability < prdct.MIN_PROBABILITY: 
48                              suggestion.probability = prdct.MIN_PROBABILITY 
49                  seen_tokens.add(token) 
50                  result.add_suggestion(suggestion) 
51          return result 
52   
53      @abc.abstractmethod 
54 -    def combine(self, predictionList): 
55          """Method for combining predictors's prediction list. 
56   
57          The combine() method is the main method of the Combiner. It must be 
58          implemented by every combiners. 
59          """ 
60          raise NotImplementedError("Method must be implemented") 
61   
62   
63 -class ProbabilisticCombiner(Combiner): 
64      """Simple combiner which combine suggestions based on their probabilities. 
65   
66      This combiner does not modify the suggestions probabilities. Thus, they are 
67      sorted in descending order according to their probabilities. 
68   
69      G{classtree ProbabilisticCombiner} 
70      """ 
71 -    def __init__(self): 
72          """ProbabilisticCombiner creator.""" 
73          super(self.__class__, self).__init__() 
74          self.name = 'ProbabilisticCombiner' 
75   
76 -    def combine(self, predictionList): 
77          """Combine the suggestions in a single list and sort them. 
78   
79          @param predictionList: 
80              The list of Prediction instances. Each predictors return a 
81              Prediction instance which is added to the list by the 
82              PredictorActivator. 
83          @type predictionList: list 
84   
85          @return: 
86              The combined Prediction instance containing every suggestions of 
87              every Prediction instances sorted in descending order according to 
88              their probabilities. 
89          @rtype: L{prdct.Prediction} 
90          """ 
91          result = prdct.Prediction() 
92          for prediction in predictionList: 
93              for suggestion in prediction: 
94                  result.add_suggestion(suggestion) 
95          return(self.filter(result)) 
96