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# Natural Language Toolkit: Classifier Interface # # Copyright (C) 2001-2012 NLTK Project # Author: Edward Loper <edloper@gradient.cis.upenn.edu> # Steven Bird <sb@csse.unimelb.edu.au> (minor additions) # URL: <http://www.nltk.org/> # For license information, see LICENSE.TXT
Interfaces for labeling tokens with category labels (or "class labels").
``ClassifierI`` is a standard interface for "single-category classification", in which the set of categories is known, the number of categories is finite, and each text belongs to exactly one category.
``MultiClassifierI`` is a standard interface for "multi-category classification", which is like single-category classification except that each text belongs to zero or more categories. """
##////////////////////////////////////////////////////// #{ Classification Interfaces ##//////////////////////////////////////////////////////
""" A processing interface for labeling tokens with a single category label (or "class"). Labels are typically strs or ints, but can be any immutable type. The set of labels that the classifier chooses from must be fixed and finite.
Subclasses must define: - ``labels()`` - either ``classify()`` or ``batch_classify()`` (or both)
Subclasses may define: - either ``prob_classify()`` or ``batch_prob_classify()`` (or both) """ """ :return: the list of category labels used by this classifier. :rtype: list of (immutable) """ raise NotImplementedError()
""" :return: the most appropriate label for the given featureset. :rtype: label """ if overridden(self.batch_classify): return self.batch_classify([featureset])[0] else: raise NotImplementedError()
""" :return: a probability distribution over labels for the given featureset. :rtype: ProbDistI """ return self.batch_prob_classify([featureset])[0] else:
""" Apply ``self.classify()`` to each element of ``featuresets``. I.e.:
return [self.classify(fs) for fs in featuresets]
:rtype: list(label) """
""" Apply ``self.prob_classify()`` to each element of ``featuresets``. I.e.:
return [self.prob_classify(fs) for fs in featuresets]
:rtype: list(ProbDistI) """
""" A processing interface for labeling tokens with zero or more category labels (or "labels"). Labels are typically strs or ints, but can be any immutable type. The set of labels that the multi-classifier chooses from must be fixed and finite.
Subclasses must define: - ``labels()`` - either ``classify()`` or ``batch_classify()`` (or both)
Subclasses may define: - either ``prob_classify()`` or ``batch_prob_classify()`` (or both) """ """ :return: the list of category labels used by this classifier. :rtype: list of (immutable) """ raise NotImplementedError()
""" :return: the most appropriate set of labels for the given featureset. :rtype: set(label) """ if overridden(self.batch_classify): return self.batch_classify([featureset])[0] else: raise NotImplementedError()
""" :return: a probability distribution over sets of labels for the given featureset. :rtype: ProbDistI """ if overridden(self.batch_prob_classify): return self.batch_prob_classify([featureset])[0] else: raise NotImplementedError()
""" Apply ``self.classify()`` to each element of ``featuresets``. I.e.:
return [self.classify(fs) for fs in featuresets]
:rtype: list(set(label)) """ return [self.classify(fs) for fs in featuresets]
""" Apply ``self.prob_classify()`` to each element of ``featuresets``. I.e.:
return [self.prob_classify(fs) for fs in featuresets]
:rtype: list(ProbDistI) """ return [self.prob_classify(fs) for fs in featuresets]
# # [XX] IN PROGRESS: # class SequenceClassifierI(object): # """ # A processing interface for labeling sequences of tokens with a # single category label (or "class"). Labels are typically # strs or ints, but can be any immutable type. The set # of labels that the classifier chooses from must be fixed and # finite. # """ # def labels(self): # """ # :return: the list of category labels used by this classifier. # :rtype: list of (immutable) # """ # raise NotImplementedError()
# def prob_classify(self, featureset): # """ # Return a probability distribution over labels for the given # featureset.
# If ``featureset`` is a list of featuresets, then return a # corresponding list containing the probability distribution # over labels for each of the given featuresets, where the # *i*\ th element of this list is the most appropriate label for # the *i*\ th element of ``featuresets``. # """ # raise NotImplementedError()
# def classify(self, featureset): # """ # Return the most appropriate label for the given featureset.
# If ``featureset`` is a list of featuresets, then return a # corresponding list containing the most appropriate label for # each of the given featuresets, where the *i*\ th element of # this list is the most appropriate label for the *i*\ th element # of ``featuresets``. # """ # raise NotImplementedError()
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