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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
from sqlalchemy.orm import sessionmaker, scoped_session
from sqlalchemy import ForeignKey
from sqlalchemy.orm import relationship, backref
import correlation
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)
age = Column(Integer, nullable=True)
gender = Column(String(2), nullable=True)
occupation = Column(String(64), nullable=True)
zipcode = Column(String(15), nullable=True)
email = Column(String(200), nullable=True)
password = Column(String(64), nullable=True)
def similarity(user1, user2):
u_ratings = {}
paired_ratings = []
for r in user1.ratings:
u_ratings[r.movie_id] = r
for r in user2.ratings:
u_r = u_ratings.get(r.movie_id)
if u_r:
paired_ratings.append((u_r.rating, r.rating))
if paired_ratings:
return correlation.pearson(paired_ratings)
else:
return 0.0
def predict_rating(self, movie):
ratings = self.ratings
other_ratings = movie.ratings
similarities = [(self.similarity(r.user), 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 Movies(Base):
__tablename__ = "movies"
id = Column(Integer, primary_key=True)
name = Column(String(140))
released_at = Column(String(64))
imdb_url = Column(String(300))
class Ratings(Base):
__tablename__ = "ratings"
id = Column(Integer, primary_key=True)
user_id = Column(Integer(64), ForeignKey('users.id'))
movie_id = Column(Integer(64), ForeignKey('movies.id'))
rating = Column(Integer(64))
user = relationship("User", backref=backref("ratings", order_by=id))
movies = relationship("Movies", backref=backref("ratings", order_by=id))
### End class declarations
def main():
pass
if __name__ == "__main__":
main()