1. Python ORMs
Cosmin Poieana
<cmin@ropython.org>
→ baze de date
→ tipuri de ORM (modele)
→ comparații (exemple)
→ peewee
→ resurse

2. Database APIs
NoSQL
● redis
● mongodb
● …
SQL
● pyodbc
● sqlite3
● pymysql
● ...

3. sqlite3
● Nu are nevoie de driver, server
● Static pe disc / memorie
● Interogări simple (+ mici diferențe)
1. conexiune
2. obținere cursor
3. execuție interogare
*. commit
4. închidere

4. sqlite3
>>> import sqlite3
>>> conn = sqlite3.connect("ropy.db")
>>> c = conn.cursor()
>>> c.execute("CREATE TABLE persoana (nume text,
adresa text, varsta real)")
>>> c.execute("INSERT INTO persoana VALUES
('Nume1', 'Adresa1', 20)")
>>> conn.commit()
>>> c.execute("SELECT * FROM persoana")
>>> c.fetchall()
[(u'Nume1', u'Adresa1', 20.0)]

5. ORM
● Object-relational mapping
(convertire date dintr-un sistem incompatibil in
POO)
● Pony, Django ORM, peewee, SQLAlchemy
● Modele
– DataMapper
– ActiveRecord
● SQLite, MySQL, PostgreSQL[, Oracle]

6. Django ORM
$ django-admin.py startproject ropy
$ cd ropy
$ python manage.py syncdb
>>> from django.db import models
>>> class Person(models.Model):
... name = models.TextField()
... class Meta:
... app_label = 'demo'
>>> class Address(models.Model):
... address = models.TextField()
... person = models.ForeignKey(Person)
... class Meta:
... app_label = 'demo'

7. Django ORM
>>> p = Person(name='person')
>>> p.save()
>>> print "%r, %r" % (p.id, p.name)
1, 'person'
>>> a = Address(person=p, address='address')
>>> a.save()
>>> print "%r, %r" % (a.id, a.address)
1, 'address'

8. Django ORM
>>> persons = Person.objects.filter(name='person')
>>> p = persons[0]
>>> print "%r, %r" % (p.id, p.name)
1, u'person'
>>> addresses = Address.objects.filter(person=p)
>>> addresses
[<address>]
>>> a = addresses[0]
>>> print "%r, %r" % (a.id, a.address)
1, u'address'

9. Peewee
>>> from peewee import SqliteDatabase, CharField,
ForeignKeyField, Model
>>> db = SqliteDatabase(':memory:')
>>> class Person(Model):
... name = CharField()
... class Meta:
... database = db
>>> class Address(Model):
... address = CharField()
... person = ForeignKeyField(Person)
... class Meta:
... database = db
>>> Person.create_table()
>>> Address.create_table()

10. Peewee
>>> p = Person(name='person')
>>> p.save()
>>> a = Address(address='address',
person=p)
>>> a.save()

11. Peewee
>>> person = Person.select().where(Person.name ==
'person').get()
>>> print '%r, %r' % (person.id, person.name)
1, u'person'
>>> address = Address.select().where(Address.person ==
person).get()
>>> print '%r, %r' % (address.id, address.address)
1, u'address'

12. Resurse
● http://www.pythoncentral.io/sqlalchemy-vs-orms/
● http://peewee.readthedocs.org/en/latest/
● http://effectivedjango.com/orm.html
● http://www.sqlalchemy.org/
● http://ponyorm.com/