omen2

Simple library that makes working with classes and databases more convenient in python.

omen2 will take a set of classes, and a database, and link them together.

omen2 allows the user to:

serialize created objects to the db
query the db and return objects, not rows
query for related objects
access/lock/update singleton objects across multiple threads
roll back changes on exceptions
create objects not-bound to the db, and later, bind them
cache objects in use, flexible cache-control

omen2 is not fully flexible with regards to database structure:

related tables must have primary keys

from notanorm import SqliteDb
from omen2 import Omen

class MyOmen(Omen):
    version = 2

    @staticmethod
    def schema(version):
        # use an omen2-compatible schema, which is a semicolon-delimited sqlite-compatible create statement
        return """create table cars(id integer primary key, color text not null, gas_level double default 1.0);
                  create table doors(carid integer, type text, primary key (carid, type));"""
        
        # or, just return a list of type-annotated classes derived from ObjBase

        # or, don't have one at all, it's ok

# you don't have to codegen, you can also just derive from omen2.ObjBase
# but you have to match your database system to the model one way or another
# either manual, codegen, or dbgen
MyOmen.codegen()

# assuming this is example.py
import example_gen as gen_objs

# every table has a row_type, you can derive from it
class Car(gen_objs.cars_row):
    def __init__(self, color="black", **kws):
        self.not_saved_to_db = "some thing"
        self.doors = gen_objs.doors_relation(self, kws.pop("doors", None), carid=lambda: self.id)
        super().__init__(color=color, **kws)

    @property
    def gas_pct(self):
        # read only props are fine
        return self.gas_level * 100


# if you're using code generation, every db table has a type, you can derive from it
class Cars(gen_objs.cars):
    # feel free to redefine the row_type used
    row_type = Car


db = SqliteDb(":memory:")

mgr = MyOmen(db, cars=Cars)

# there's always a mapping from table class to instance
# so Omen knows what classes are in charge of what tables
mgr.cars = mgr[Cars]

# fine too (or stick in init)
mgr.cars = Cars(self)

# by default, you can always iterate on tables
assert mgr.cars.count() == 0

car = Car()         # creates a default car (black, full tank)
car.color = "red"
car.gas_level = 0.5

# you don't need to create a class, if you use the code-generated one
car.doors.add(gen_objs.doors_row(type="a"))
car.doors.add(gen_objs.doors_row(type="b"))
car.doors.add(gen_objs.doors_row(type="c"))
car.doors.add(gen_objs.doors_row(type="d"))
mgr.cars.add(car)

# cars have ids, generated by the db
assert car.id

mgr.cars.add(Car(color="red", gas_level=0.3, doors=[gen_objs.doors_row(type=str(i)) for i in range(4)]))

assert sum(1 for _ in mgr.cars.select(color="red")) == 2    # 2

print("cars:", list(mgr.cars.select(color="red")))

car = mgr.cars.select_one(color="red", gas_level=0.3)

with car:
    car.gas_level = 0.9

assert len(car.doors) == 4

To run codegen manually, rather than "inline", you can run: omen2-codegen my.package.MyClassName.

Commiting this file, and running this as a git-hook on any change is a useful pattern.

Metadata

Release files for omen2 2.1.5

For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.

Built distribution (wheel)

Table of built distributions (wheels) for omen2 2.1.5
File	Interpreter	ABI	Platform	Reset
omen2-2.1.5-py3-none-any.whl 28.8 kB Jan 25, 2023	Python 3	none	any	Details

Release files / omen2-2.1.5-py3-none-any.whl

Download URL	omen2-2.1.5-py3-none-any.whl
Size	28.8 kB
Tags	Python 3
SHA-256 checksum How to use checksums	`09e8b1eda58f5ffa32eaba76e876b16911f9ff60cf9363c0db384adf588aaec2`
BLAKE2b-256 checksum How to use checksums	`83d8352be42c15edb2f25ec1c41448cb76db53f9f4d7a09c1e269fc2930679a5`
Upload date	Jan 25, 2023
Uploaded using Trusted Publishing? What is trusted publishing?	No
Uploaded via	`twine/3.3.0 pkginfo/1.7.0 requests/2.27.1 setuptools/46.0.0 requests-toolbelt/0.9.1 tqdm/4.32.2 CPython/3.6.9`