Add Session context manager

[Chris Herrick]

It would be very nice if the Session object had a context manager similar to the following:

def __enter__(self):
    return self

def __exit__(self, type, value, traceback):
    self.flush()

[Mike Bayer]

the usual context manager use w/ Session is:

with session.transaction:
    # code

that's already there (it needs to be in the documentation though). It does a commit() at the end. flush() is awkward because you should already be using autoflush; calling flush() manually is not very common. Does this suit your use case?

[Mike Bayer]

reopen if this use case can be identified.

[Chris Herrick]

The following approach is still awkward (although very valid).

session = makesession()
with session.transaction:
   # code

I would find the following to be more intuitive and useful.

with sessionmaker() as session:
   # code

This may be personal preference.

[Mike Bayer]

What happens at the end of that contextmanager ?

[Mike Bayer]

also, does it help that you can subclass Session and make any context managers you want ?