ORMar

The ormar package is an async ORM for Python, with support for Postgres, MySQL, and SQLite. Ormar is built with:

• SQLAlchemy core for query building.
• databases for cross-database async support.
• pydantic for data validation.

Because ormar is built on SQLAlchemy core, you can use alembic to provide database migrations.

The goal was to create a simple ORM that can be used directly with fastapi that bases it's data validation on pydantic. Initial work was inspired by encode/orm, later I found ormantic and used it as a further inspiration. The encode package was too simple (i.e. no ability to join two times to the same table) and used typesystem for data checks.

ormar is still under development: We recommend pinning any dependencies with ormar~=0.2.0

Note: Use ipython to try this from the console, since it supports await.

import databases
import ormar
import sqlalchemy

database = databases.Database("sqlite:///db.sqlite")
metadata = sqlalchemy.MetaData()


class Note(ormar.Model):
    class Meta:
        tablename = "notes"
        database = database
        metadata = metadata

    # primary keys of type int by dafault are set to autoincrement    
    id: ormar.Integer(primary_key=True)
    text: ormar.String(length=100)
    completed: ormar.Boolean(default=False)

# Create the database
engine = sqlalchemy.create_engine(str(database.url))
metadata.create_all(engine)

# .create()
await Note.objects.create(text="Buy the groceries.", completed=False)
await Note.objects.create(text="Call Mum.", completed=True)
await Note.objects.create(text="Send invoices.", completed=True)

# .all()
notes = await Note.objects.all()

# .filter()
notes = await Note.objects.filter(completed=True).all()

# exact, iexact, contains, icontains, lt, lte, gt, gte, in
notes = await Note.objects.filter(text__icontains="mum").all()

# .get()
note = await Note.objects.get(id=1)

# .update()
await note.update(completed=True)

# .delete()
await note.delete()

# 'pk' always refers to the primary key
note = await Note.objects.get(pk=2)
note.pk  # 2

Ormar supports loading and filtering across foreign keys...

import databases
import ormar
import sqlalchemy

database = databases.Database("sqlite:///db.sqlite")
metadata = sqlalchemy.MetaData()


class Album(ormar.Model):
    class Meta:
        tablename = "album"
        metadata = metadata
        database = database

    id: ormar.Integer(primary_key=True)
    name: ormar.String(length=100)


class Track(ormar.Model):
    class Meta:
        tablename = "track"
        metadata = metadata
        database = database

    id: ormar.Integer(primary_key=True)
    album: ormar.ForeignKey(Album)
    title: ormar.String(length=100)
    position: ormar.Integer()


# Create some records to work with.
malibu = await Album.objects.create(name="Malibu")
await Track.objects.create(album=malibu, title="The Bird", position=1)
await Track.objects.create(album=malibu, title="Heart don't stand a chance", position=2)
await Track.objects.create(album=malibu, title="The Waters", position=3)

fantasies = await Album.objects.create(name="Fantasies")
await Track.objects.create(album=fantasies, title="Help I'm Alive", position=1)
await Track.objects.create(album=fantasies, title="Sick Muse", position=2)


# Fetch an instance, without loading a foreign key relationship on it.
track = await Track.objects.get(title="The Bird")

# We have an album instance, but it only has the primary key populated
print(track.album)       # Album(id=1) [sparse]
print(track.album.pk)    # 1
print(track.album.name)  # Raises AttributeError

# Load the relationship from the database
await track.album.load()
assert track.album.name == "Malibu"

# This time, fetch an instance, loading the foreign key relationship.
track = await Track.objects.select_related("album").get(title="The Bird")
assert track.album.name == "Malibu"

# By default you also get a second side of the relation 
# constructed as lowercase source model name +'s' (tracks in this case)
# you can also provide custom name with parameter related_name
album = await Album.objects.select_related("tracks").all()
assert len(album.tracks) == 3

# Fetch instances, with a filter across an FK relationship.
tracks = Track.objects.filter(album__name="Fantasies")
assert len(tracks) == 2

# Fetch instances, with a filter and operator across an FK relationship.
tracks = Track.objects.filter(album__name__iexact="fantasies")
assert len(tracks) == 2

# Limit a query
tracks = await Track.objects.limit(1).all()
assert len(tracks) == 1

Data types

The following keyword arguments are supported on all field types.

• primary_key
• nullable
• default
• server_default
• index
• unique

All fields are required unless one of the following is set:

• nullable - Creates a nullable column. Sets the default to None.
• default - Set a default value for the field.
• server_default - Set a default value for the field on server side (like sqlalchemy's func.now()).
• primary key with autoincrement - When a column is set to primary key and autoincrement is set on this column. Autoincrement is set by default on int primary keys.

Available Model Fields:

• String(length)
• Text()
• Boolean()
• Integer()
• Float()
• Date()
• Time()
• DateTime()
• JSON()
• BigInteger()
• Decimal(lenght, precision)