How do I write a three-block context manager in Python?

问题

I have many functions that exploit the context manager pattern:

@contextmanager
def f():
    # Do preliminary stuff.
    yield
    # Do final stuff.

I use an ExitStack to call all of these context managers.

I am considering the pattern:

@threeblock_contextmanager
def f():
    # Do preliminary stuff.
    yield
    # Do intermediary stuff.
    yield
    # Do final stuff.

I've been looking at the source and thought I would modify it in some way. Is there a nice way to accomplish this? My other option is to add a method to each class that returns a context manager. The disadvantage of adding a method is that the intuitive linear view of the code is lost because the intermediary stuff will be in a different method rather than placed between the preliminary and final stuff, which I consider more logical.

As requested, more code:

def fire(self, cluster_index, obs_count=1.0):
    with ExitStack() as stack:
        for link in self.terminal.out:
            stack.enter_context(
                link.source_firing(cluster_index, obs_count))
        for link in self.terminal.in_:
            stack.enter_context(
                link.target_firing(cluster_index, obs_count))

        # At this point all context managers have been run up until
        # their yield.   They saw a signal that was neither updated at
        # the source nor the target.

        # Update signals.

        # TODO: at this point, the context managers need to send any signals they
        # want to send and yield again.

    # At this point all context managers have been run entirely.
    # On closing, they saw a signal has been updated at both the source
    # and the receiver.

    self.ask_for_reschedule()

来源：https://stackoverflow.com/questions/24424980/how-do-i-write-a-three-block-context-manager-in-python

标签

python

contextmanager