Context manager on method call from class

Thu Mar 15 14:17:31 EDT 2018

I have a class which implements a context manager, its __init__
has a signature and the __enter__ returns an instance of the
class.
Along with several methods which implement functionality on
the instance, I have one method which itself must open a context
manager against a call on an instance attribute. This context manager
does not return an instance of itself, it merely opens a context.
I am not thrilled about is the implementation I have used and I
am wondering if there is a better way. It's been a long time since
I have worked in Python and I am probably overlooking something
obvious. Syntactically I achieve what I want in use, but it looks awkward
in its implementation. How can I clean up the first class and decorator
to implement the functionality on a method in the Foo class?
class MethodContextManager:
 def __init__(self, obj, key, value):
 self.obj = obj
 self.key = key
 self.value = value
 def __enter__(self):
 self.obj.some_method(key, value)
 def __exit__(self, exc_type, exc_val, exc_tb):
 self.obj.another_method()
def method_context_manager(func):
 def wrapper(self, key, value):
 return MethodContextManager(self.instance, key, value)
 return wrapper
class Foo:
 def __init__(self, bar):
 self.bar = bar
 self.instance = None
 def __enter__(self):
 self.instance = SomeFunc(this.bar)
 return self
 def __exit__(self, exc_type, exc_val, exc_tb):
 # Cleanup...
 @method_context_manager
 def baz(self, key, value):
 pass
with Foo(bar) as foo:
 foo.other_call()
 with foo.baz(42, "a"):
 foo.other_call()
 with foo.baz(420, None):
 foo.other_call()
 foo.other_call()
 foo.other_call()
 foo.other_call()