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A sensible orm for PostgreSQL or SQLite

Project description


An opinionated lightweight orm for PostgreSQL or SQLite.

Prom has been used in both single threaded and multi-threaded environments, including environments using Greenthreads.

1 Minute Getting Started with SQLite

First, install prom:

$ pip install prom

Set an environment variable:

$ export PROM_DSN=sqlite://:memory:

Start python:

$ python

Create a prom Orm:

>>> import prom
>>> class Foo(prom.Orm):
...     table_name = "foo_table_name"
...     bar = prom.Field(int)

Now go wild and create some Foo objects:

>>> for x in range(10):
...     f = Foo.create(bar=x)

Now query them:

>>> f =
>>> for f in Foo.query.in_bar([3, 4, 5]):

Update them:

>>> for f in Foo.query:
... += 100

and get rid of them:

>>> for f in Foo.query:
...     f.delete()

Congratulations, you have now created, retrieved, updated, and deleted from your database.


Prom can be automatically configured on import by setting the environment variable PROM_DSN.

The PROM_DSN should define a dsn url:


The built-in interface classes don't need their full python paths, you can just use sqlite and postgres.

So to use the builtin Postgres interface on testdb database on host localhost with username testuser and password testpw:


And to set it in your environment:

export PROM_DSN=postgres://testuser:testpw@localhost/testdb

After you've set the environment variable, then you just need to import Prom in your code:

import prom

and Prom will take care of parsing the dsn url(s) and creating the connection(s) automatically.

Multiple db interfaces or connections

If you have multiple connections, you can actually set multiple environment variables:

export PROM_DSN_1=postgres://testuser:testpw@localhost/testdb1#conn_1
export PROM_DSN_2=sqlite://testuser:testpw@localhost/testdb2#conn_2

It's easy to have one set of prom.Orm children use one connection and another set use a different connection, since the fragment part of a Prom dsn url sets the name:

import prom


class Orm1(prom.Orm):
    connection_name = "connection_1"
class Orm2(prom.Orm):
    connection_name = "connection_2"

Now, any child class that extends Orm1 will use connection_1 and any child class that extends Orm2 will use connection_2.

Creating Models

Checkout the README to see how to define the db schema and create models your python code can use.

Querying Rows

Checkout the README to see how to perform queries on the db.


While Prom will most likely work on other versions, Prom is tested to work on 2.7+ and 3.8.



If you want to use Prom with Postgres, you need psycopg2:

$ apt-get install libpq-dev python-dev
$ pip install psycopg

Green Threads

If you want to use Prom with gevent, you'll need gevent and psycogreen:

$ pip install gevent
$ pip install psycogreen

These are the versions we're using:

$ pip install "gevent==20.6.2"
$ pip install "psycogreen==1.0"

Then you can setup Prom like this:

from prom.interface.postgres import gevent

Now you can use Prom in the same way you always have. If you would like to configure the threads and stuff, you can pass in some configuration options using the dsn, the three parameters are async, pool_maxconn, pool_minconn, and pool_class. The only one you'll really care about is pool_maxconn which sets how many connections should be created.


Prom installs using pip:

$ pip install prom

and to install the latest and greatest:

$ pip install --upgrade "git+"

Using for the first time

Prom takes the approach that you don't want to be hassled with table installation while developing, so when it tries to do something and sees that the table doesn't yet exist, it will use your defined fields for your prom.model.Orm child and create a table for you, that way you don't have to remember to run a script or craft some custom db query to add your tables. Prom takes care of that for you automatically.

Likewise, if you add a field (and the field is not required) then prom will go ahead and add that field to your table so you don't have to bother with crafting ALTER queries while developing.

If you want to install the tables manually, you can create a script or something and use the Orm's install() method:


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