MongoDB backend class for a document filter on https://bitbucket.org/knzm/collective/src/default/ch6/docclass.py.

mongodb_backend.py

class MongoDBBackend(object):
    def __init__(self, db, user):
        self.db = db
        self.user = user

    def inc_feature(self, feature, cat):
        """特徴 feature がカテゴリ cat に出現した回数を 1 増やす"""
        features = self.db.features.find({'user': self.user,
                                          'feature': feature,
                                          'category': cat})
        if features.count():
            self.db.features.update({'user': self.user,
                                     'feature': feature,
                                     'category': cat},
                                    {'$inc': {'count': 1.0}})
        else:
            self.db.features.insert({'user': self.user,
                                     'feature': feature,
                                     'category': cat,
                                     'count': 1.0})

    def inc_category(self, cat):
        """カテゴリ cat が出現した回数を 1 増やす"""
        categories = self.db.categories.find({'user': self.user,
                                              'category': cat})
        if categories.count():
            self.db.categories.update({'user': self.user,
                                       'category': cat},
                                      {'$inc': {'count': 1}})
        else:
            self.db.categories.insert({'user': self.user,
                                       'category': cat,
                                       'count': 1})

    def get_feature_count(self, f, cat):
        """特徴 feature がカテゴリ cat に出現した回数を返す"""
        feature = self.db.features.find_one({'user': self.user,
                                             'feature': f,
                                             'category': cat})
        if feature:
            return float(feature['count'])
        else:
            return 0.0

    def get_cat_count(self, cat):
        """カテゴリ cat が出現した回数を返す"""
        category = self.db.categories.find_one({'user': self.user,
                                                'category': cat})
        if category:
            return category['count']
        else:
            return 0

    def total_count(self):
        """すべてのカテゴリの出現回数を返す"""
        r = self.db.categories.aggregate([
            {'$group': {'_id': None,
             'total': {'$sum': '$count'}}}
        ])
        return r['result'][0]['total']

    def categories(self):
        """すべてのカテゴリのリストを返す"""
        return map(lambda x: x['category'],
                   self.db.categories.find({'user': self.user}))

    def commit(self):
        """学習結果を保存する"""
        pass