On 01/24/2017 01:31 PM, This Wiederkehr wrote:

having a class definition:

class Test():

@classmethod
def __enter__(cls):
     pass

@classmethod
def __exit__(cls, exception_type, execption_value, callback):
     pass

now using this as a contextmanager does not work, even though Test is an
object and has the two required methods __enter__ and __exit__.

It is not working because you are trying to use the class itself, and not it's 
instances, as a context manager (which also means you don't need classmethod):

Wrong:

  with Test:

Correct:

  with Test():

I am asking because I'd like to implement the clean up behaviour for
multiple instances directly into the class:

with Test:
    testinstance1 = Test()
    testinstance2 = Test()
# on context exit Test.__exit__ should take care on cleaning up
testinstance1 and testinstance2.

You might be able to make this work with a custom type (aka using a custom 
metaclass) -- but that could be a bunch of work.

--
~Ethan~
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