transaction manager recipe for pyramid sqlalchemy session

delicious_recipe.py

from contextlib import contextmanager
from functools import singledispatch, partial
from pathlib import Path

import pkg_resources


# development config uri for base distribution
DEVELOPMENT_CONFIG_URI = pkg_resources. \
    get_distribution('distribution_package_name').get_resource_filename(
    pkg_resources.ResourceManager(),
    'development.ini'
)

@contextmanager
@singledispatch
def dbsession(settings):
    """
    A context manager that allows us to connect to the database
    given pastedeploy settings.

    i.e.

    from pyramid.paster import get_appsettings
    import pyramid_project.models as models

    config_uri = '/path/to/development.ini'
    settings = get_appsettings(config_uri)
    with models.dbsession(settings) as session:
        ... do stuff

    """
    engine = get_engine(settings)
    session_factory = get_session_factory(engine)
    with transaction.manager:
        session = get_tm_session(session_factory, transaction.manager)
        yield session


@dbsession.register(str)
def _(config_uri):
    """
    Given a path to a configuration file, yield a dbsession.
    
    i.e.

    import pyramid_project.models as models

    config_uri = '/path/to/development.ini'
    with models.dbsession(config_uri) as session:
        ... do stuff
    """
    path = Path(config_uri)
    settings = get_appsettings(str(path.absolute()))
    with dbsession(settings) as session:
        yield session

# default context manager for use during development
development_session = partial(dbsession, DEVELOPMENT_CONFIG_URI)