24/4/2018 SQLAlchemy

Flow of building connection with database via SQLAlchemy

Create Engine

Step	Key Code	Inspect
Connecting	>>> from sqlalchemy import create_engine >>> engine = create_engine('sqlite:///:memory:', echo=True)
Map Declare	>>> from sqlalchemy.ext.declarative import declarative_base >>> Base = declarative_base()
	>>> from sqlalchemy import Column, Integer, String >>> class User(Base): ... __tablename__ = 'users' ... ... id = Column(Integer, primary_key=True) ... name = Column(String) ... fullname = Column(String) ... password = Column(String) ... ... def __repr__(self): ... return "<User(name='%s', fullname='%s', password='%s')>" % ( ... self.name, self.fullname, self.password)	>>> User.__table__ Table('users', MetaData(bind=None), Column('id', Integer(), table=<users>, primary_key=True, nullable=False), Column('name', String(), table=<users>), Column('fullname', String(), table=<users>), Column('password', String(), table=<users>), schema=None)

18/4/2018 SQLAlchemy

Engine

To connect a database, use create_engine() from sqlalchemy. The create_engine() function produce an engine object based on a URL. The URLs follow RFC-1738.

>>>engine = create_engine(dialect+driver://username:password@host:port/database)

The above engine creates a Dialect object tailored towards the database and creates a Pool object which establish a DBAPI connection. However, it's first still not yet established until  Engine.connect()  method is called or an operation which is dependent on this method such as Engine.execute() is invoked.

17/04/2018 SQLAlchemy

SQLAlchemy

Consists of two components

• Core = a fully featured SQL abstraction toolkit, providing a smooth layer of abstraction over a wide variety of DBAPI implementations and behaviors, as well as a SQL Expression Language which allows expression of the SQL language via generative Python expressions
• ORM = Object Relational Mapper