util.py 文件源码

def extract_unigram_feats(document, unigrams, handle_negation=False):
    """
    Populate a dictionary of unigram features, reflecting the presence/absence in
    the document of each of the tokens in `unigrams`.

    :param document: a list of words/tokens.
    :param unigrams: a list of words/tokens whose presence/absence has to be
        checked in `document`.
    :param handle_negation: if `handle_negation == True` apply `mark_negation`
        method to `document` before checking for unigram presence/absence.
    :return: a dictionary of unigram features {unigram : boolean}.

    >>> words = ['ice', 'police', 'riot']
    >>> document = 'ice is melting due to global warming'.split()
    >>> sorted(extract_unigram_feats(document, words).items())
    [('contains(ice)', True), ('contains(police)', False), ('contains(riot)', False)]
    """
    features = {}
    if handle_negation:
        document = mark_negation(document)
    for word in unigrams:
        features['contains({0})'.format(word)] = word in set(document)
    return features