Efficiently updating database using SQLAlchemy ORM

Question

I\'m starting a new application and looking at using an ORM -- in particular, SQLAlchemy.

Say I\'ve got a column \'foo\' in my database and I want to increment it.

Answer 1

Here's an example of how to solve the same problem without having to map the fields manually:

from sqlalchemy import Column, ForeignKey, Integer, String, Date, DateTime, text, create_engine
from sqlalchemy.exc import IntegrityError
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from sqlalchemy.orm.attributes import InstrumentedAttribute

engine = create_engine('postgres://postgres@localhost:5432/database')
session = sessionmaker()
session.configure(bind=engine)

Base = declarative_base()


class Media(Base):
  __tablename__ = 'media'
  id = Column(Integer, primary_key=True)
  title = Column(String, nullable=False)
  slug = Column(String, nullable=False)
  type = Column(String, nullable=False)

  def update(self):
    s = session()
    mapped_values = {}
    for item in Media.__dict__.iteritems():
      field_name = item[0]
      field_type = item[1]
      is_column = isinstance(field_type, InstrumentedAttribute)
      if is_column:
        mapped_values[field_name] = getattr(self, field_name)

    s.query(Media).filter(Media.id == self.id).update(mapped_values)
    s.commit()

So to update a Media instance, you can do something like this:

media = Media(id=123, title="Titular Line", slug="titular-line", type="movie")
media.update()