half-orm 1.0.0rc1

A simple PostgreSQL to Python mapper.

halfORM

⚠️ BREAKING CHANGES in v1.0.0-a1

ho_get() is now public and returns a dict directly. It raises NotFoundError (0 rows) or MultipleRowsError (> 1 row) instead of counting first.

Deprecated query-builder setters removed — ho_limit, ho_offset, ho_order_by, ho_distinct no longer exist as setters. Pass these as keyword arguments to ho_select():

# Before (0.x)
rel.ho_limit = 10
rel.ho_order_by = 'name'
list(rel)

# After (1.0)
list(rel.ho_select(limit=10, order_by='name'))

FKEYS_PROPERTIES / FKEYS class attributes removed — use Fkeys only.

ho_cast() now raises CastError if the target is not in the PostgreSQL inheritance hierarchy of the relation.

See CHANGELOG.md for the full list of changes.

halfORM is a database-first ORM for PostgreSQL. You write the schema in SQL; halfORM introspects it at runtime and gives you Python objects to work with your data. No migrations, no code generation.

The central idea: a Relation object is a predicate. It describes the logical condition that rows must satisfy to belong to the relation. Its extension — the set of rows currently satisfying the predicate in the database — is what you read, update, or delete.

Key features

• Database-first — the schema lives in PostgreSQL, not in Python classes.
• Predicate model — relations are predicates; set operators (|, &, -) compose them before any SQL is sent.
• FK navigation — join across tables (and views) by setting FK attributes; explicit Fkeys dict for views where PostgreSQL stores no FK metadata.
• Sync + async — every executor has an a-prefixed async counterpart (ho_aselect, ho_ainsert, …).
• Bulk load — ho_copy / ho_acopy for high-throughput inserts via PostgreSQL COPY.
• No magic — queries are built from the predicate you describe and executed only when you call an executor. ho_mogrify() shows the exact SQL.

Install

pip install half_orm

Requires psycopg 3 (psycopg[binary]).

Configure

# ~/.half_orm/blog
[database]
name     = blog
user     = alice
password = secret
host     = localhost

Usage

from half_orm.model import Model
from half_orm.relation_errors import NotFoundError, MultipleRowsError

blog   = Model('blog')
Post   = blog.get_relation_class('blog.post')
Author = blog.get_relation_class('blog.author')

# Insert — returns the inserted row as a dict
alice = Author(
    first_name='Alice', last_name='Martin', email='[e-mail]'
).ho_insert()

# Query — Author(last_name='Martin') is a predicate, not a query
for row in Author(last_name='Martin').ho_select('id', 'email'):
    print(row)

# Get exactly one row
try:
    author = Author(last_name='Martin').ho_get()
except NotFoundError:
    print("no such author")
except MultipleRowsError:
    print("ambiguous — more than one author named Martin")

# FK navigation — no JOIN written by hand
post = Post(id=1)
post.author_fk.set()                         # join all authors
for row in post.ho_select(json_agg={'author_fk': ['first_name', 'last_name']}):
    print(row['author_fk'])                  # {'first_name': 'Alice', 'last_name': 'Martin'}

# Set operators — compose predicates before hitting the database
recent   = Post(created_at=('>', '2024-01-01'))
featured = Post(featured=True)
combined = recent | featured                 # UNION
print(combined.ho_count())

# Update / delete
Author(id=alice['id']).ho_update(email='[e-mail]')
Author(id=alice['id']).ho_delete()

Documentation

• Learn halfORM in half an hour
• API Reference

License

halfORM is licensed under the GPL-3.0 license.