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model.py
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model.py
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from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import create_engine
from sqlalchemy import Column, Integer, String, DateTime
from sqlalchemy.orm import sessionmaker, scoped_session
from sqlalchemy import ForeignKey
from sqlalchemy.orm import relationship, backref
import correlation
engine = None
session = None
engine = create_engine("sqlite:///ratings.db", echo=False)
session = scoped_session(sessionmaker(bind=engine,
autocommit = False,
autoflush = False))
Base = declarative_base()
Base.query = session.query_property()
### Class declarations go here
class User(Base):
__tablename__ = "users"
id = Column(Integer, primary_key = True)
email = Column(String(64), nullable=True)
password = Column(String(64), nullable=True)
age = Column(Integer, nullable=True)
zipcode = Column(String(15), nullable=True)
def similarity (user1, user2):
user1_dict = {}
pair_list = []
for r in user1.ratings:
user1_dict[r.movie_id] = r
for r in user2.ratings:
user1_rating = user1_dict.get(r.movie_id)
if user1_rating:
pair_list.append( (r.rating, user1_rating.rating) )
if pair_list:
return correlation.pearson(pair_list)
else:
return 0.0
def predict_rating(self, movie):
#movie_info is the movie object
ratings = self.ratings
other_ratings = movie.ratings
similarities = [ (movie.similarity(r.movie), r)
for r in other_ratings ]
similarities.sort(reverse = True)
similarities = [ sim for sim in similarities if sim[0] > 0 ]
if not similarities:
return None
numerator = sum([ r.rating * similarity for similarity, r in similarities ])
denominator = sum([ similarity[0] for similarity in similarities ])
return numerator/denominator
class Movie(Base):
__tablename__ = "movies"
id = Column(Integer, primary_key = True)
name = Column(String(100), nullable=False)
release_date = Column(DateTime(30), nullable=True)
imdb_url = Column(String(300), nullable=True)
def similarity (self, movie2):
self_dict = {}
pair_list = []
for r in self.ratings:
self_dict[r.user_id] = r
for r in movie2.ratings:
self_rating = self_dict.get(r.user_id)
if self_rating:
pair_list.append( (r.rating, self_rating.rating) )
if pair_list:
return correlation.pearson(pair_list)
else:
return 0.0
class Rating(Base):
__tablename__ = "ratings"
id = Column(Integer, primary_key = True)
movie_id = Column(Integer, ForeignKey('movies.id'))
user_id = Column(Integer, ForeignKey('users.id'))
rating = Column(Integer, nullable=False)
user = relationship("User",
backref=backref("ratings", order_by=id))
movie = relationship("Movie",
backref=backref("ratings", order_by=id))
### End class declarations
# def connect():
# global ENGINE
# global Session
# return Session()
def main():
"""In case we need this for something"""
pass
if __name__ == "__main__":
main()
Base.metadata.create_all(engine)