a little orm
Project description
a small orm
written to provide a lightweight querying interface over sql
uses sql concepts when querying, like joins, group by, having, etc.
Examples:
# a simple query selecting a user
User.select().where(username='charles')
# get the tweets by a user named charles and order the newest to oldest
Tweet.select().order_by(('pub_date', 'desc')).join(User).where(username='charles')
# how many active users are there?
User.select().where(active=True).count()
# paginate the user table and show me page 3 (users 41-60)
User.select().order_by(('username', 'asc')).paginate(3, 20)
# order users by number of tweets
User.select({
User: ['*'],
Tweet: [Count('id', 'num_tweets')]
}).group_by('id').join(Tweet).order_by(('num_tweets', 'desc'))
model definitions and schema creation
smells like django:
import peewee
class Blog(peewee.Model):
title = peewee.CharField()
def __unicode__(self):
return self.title
class Entry(peewee.Model):
title = peewee.CharField(max_length=50)
content = peewee.TextField()
pub_date = peewee.DateTimeField()
blog = peewee.ForeignKeyField(Blog)
def __unicode__(self):
return '%s: %s' % (self.blog.title, self.title)
gotta connect:
>>> from peewee import database >>> database.connect()
create some tables:
>>> Blog.create_table() >>> Entry.create_table()
foreign keys work like django’s
>>> b = Blog(title="Peewee's Big Adventure") >>> b.save() >>> e = Entry(title="Greatest movie ever?", content="YES!", blog=b) >>> e.save() >>> e.blog <Blog: Peewee's Big Adventure> >>> for e in b.entry_set: ... print e.title ... Greatest movie ever?
querying
queries come in 4 flavors (select/update/insert/delete).
there’s the notion of a query context which is the model being selected or joined on:
User.select().where(active=True).order_by(('username', 'asc'))
since User is the model being selected, the where clause and the order_by will pertain to attributes on the User model. User is the current query context when the .where() and .order_by() are evaluated.
an example using joins:
Tweet.select().where(deleted=False).order_by(('pub_date', 'desc')).join(
User
).where(active=True)
this will select non-deleted tweets from active users. the first .where() and .order_by() occur when Tweet is the current query context. As soon as the join is evaluated, User becomes the query context and so the following where() pertains to the User model.
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