Create sqlalchemy engines and metadata from a Django-ish set of settings.

sqlalchemy_helpers.py

from sqlalchemy import create_engine, Table
from sqlalchemy.schema import MetaData
from somewhere import settings
from collections import defaultdict

_engines = {}
_metadata = defaultdict(lambda: MetaData())
_tables = defaultdict(dict)


def db_table(content_type_name, which="default"):
    global _metadata
    global _tables
    global _engines
    if content_type_name not in _tables[which]:
        engine = get_engine(which)
        table = Table(
            content_type_name,
            _metadata[which],
            autoload=True,
            autoload_with=engine
        )
        _tables[which][content_type_name] = table
    return _tables[which][content_type_name]


def create_connect_string(which):
    tmp = '%(engine)s://%(user)s:%(password)s@%(host)s%(port)s/%(database)s'
    db = settings.DATABASES[which]
    if "postgresql" in db['ENGINE']:
        engine = "postgresql"
    elif "sqlite3" in db['ENGINE']:
        engine = "sqlite3"
    data = {
        "engine": engine,
        "host": db['HOST'] or "localhost",
        "user": db['USER'],
        "password": db['PASSWORD'],
        "port": ":" + db['PORT'] if db['PORT'] else "",
        "database": db['NAME']
    }
    return tmp % data


def get_engine(which="default"):
    global _engines
    global _metadatas
    if not _engines:
        connect_string = create_connect_string(which)
        _engines[which] = create_engine(connect_string)
        _engines[which].connect()
        _metadata[which].bind = _engines[which]
    return _engines[which]