[Python-Dev] Why are contexts also managers? (was r45544 - peps/trunk/pep-0343.txt)

[A.M. Kuchling]

On Tue, Apr 18, 2006 at 08:55:18PM +0200, phillip.eby wrote:
> Modified:
>    peps/trunk/pep-0343.txt
>
> +    "context manager" then encompasses all objects with a __context__()
> +    method that returns a context object.  (This means that all contexts
> +    are context managers, but not all context managers are contexts).

This change reminds of another question I had about the parenthetical
statement: all contexts are context managers (= 'has a __context__'
method).  Why?  The context object isn't necessarily available to the
Python programmer, so they can't write:

with context_mgr as context:
     with context:  # uses the same context
         ...

Why do contexts need to have a __context__() method?

--amk