A little background - I'm updating my entire site and used a cookiecutter
as referenced in Pyramids docs to do so. I am using sqlalchemy.
It has a db session as a request method. This works perfectly for me in all
of my views. However, I have class methods in my models that need to access
a session. I can't figure out a way to access the session that the
cookiecutter set up in models.py so I reverted to creating a separate
session using
scoped_session(sessionmaker(extension=ZopeTransactionExtension())) and
importing it into my model and using the request session in my views.
This just seems wrong - am I approaching this wrong?
Below is the model.py file that the cookiecutter created:
from sqlalchemy import engine_from_config
from sqlalchemy.orm import sessionmaker
from sqlalchemy.orm import configure_mappers
import zope.sqlalchemy
# import or define all models here to ensure they are attached to the
# Base.metadata prior to any initialization routines
from .mymodel import MyModel # flake8: noqa
# run configure_mappers after defining all of the models to ensure
# all relationships can be setup
configure_mappers()
def get_engine(settings, prefix='sqlalchemy.'):
return engine_from_config(settings, prefix)
def get_session_factory(engine):
factory = sessionmaker()
factory.configure(bind=engine)
return factory
def get_tm_session(session_factory, transaction_manager):
"""
Get a ``sqlalchemy.orm.Session`` instance backed by a transaction.
This function will hook the session to the transaction manager which
will take care of committing any changes.
- When using pyramid_tm it will automatically be committed or aborted
depending on whether an exception is raised.
- When using scripts you should wrap the session in a manager yourself.
For example::
import transaction
engine = get_engine(settings)
session_factory = get_session_factory(engine)
with transaction.manager:
dbsession = get_tm_session(session_factory, transaction.manager)
"""
dbsession = session_factory()
zope.sqlalchemy.register(
dbsession, transaction_manager=transaction_manager)
return dbsession
def includeme(config):
"""
Initialize the model for a Pyramid app.
Activate this setup using ``config.include('tutorial.models')``.
"""
settings = config.get_settings()
settings['tm.manager_hook'] = 'pyramid_tm.explicit_manager'
# use pyramid_tm to hook the transaction lifecycle to the request
config.include('pyramid_tm')
# use pyramid_retry to retry a request when transient exceptions occur
config.include('pyramid_retry')
session_factory = get_session_factory(get_engine(settings))
config.registry['dbsession_factory'] = session_factory
# make request.dbsession available for use in Pyramid
config.add_request_method(
# r.tm is the transaction manager used by pyramid_tm
lambda r: get_tm_session(session_factory, r.tm),
'dbsession',
reify=True
)
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