Decorators to handle transactional sessions : http://dev.nando.audio/2014/04/01/large_apps_with_sqlalchemy__architecture.html

sql.decorator.py

from functools import wraps

def transaction(fn):
    '''Decorator that encloses the decorated function in a DB transaction.
    The decorated function does not need to session.commit(). Usage::

        @transaction
        def my_function():  # (...)

    If any exception is raised from this function, the session is rewinded.

    But if you pass ``persist=None`` when calling your decorated function,
    the session is neither committed nor rewinded. This is great for tests
    because you are still in the transaction when asserting the result.

    If you pass ``persist=False``, the session is always rewinded.

    The default is ``persist=True``, meaning yes, commit the transaction.
    '''
    @wraps(fn)
    def wrapper(*a, **kw):
        persist = kw.pop('persist', True)
        try:
            fn(*a, **kw)
        except:
            db.session.rollback()
            raise
        else:
            if persist is False:
                db.session.rollback()
            elif persist is True:
                db.session.commit()
    return wrapper