[Python-Dev] More on contextlib - adding back a contextmanager decorator

[Nick Coghlan]

Nick Coghlan wrote:
> Greg Ewing wrote:
>> Also a thought on terminology. Even though it seems I
>> may have been the person who thought it up originally,
>> I'm not sure I like the term "manager". It seems rather
>> wooly, and it's not clear whether a "context manager"
>> is supposed to manage just one context or multiple
>> contexts.
> 
> I think getting rid of __context__ should clear up most of this confusion 
> (which is further evidence that Guido is making the right call). Once that 
> change is made, the context expression in the with statement produces a 
> context manager with __enter__ and __exit__ methods which set up and tear down 
> a managed context for the body of the with statement. This is very similar to 
> your later suggestion of context guard and guarded context.

Thinking about it a bit further. . .

1. PEP 343, 2.5 alpha 1, 2.5 alpha 2 and the discussions here have no doubt 
seriously confused the meaning of the term 'context manager' for a lot of 
people (you can certainly put me down as one such person). Anyone not already 
confused is likely to *become* confused if we subtly change the meaning in 
alpha 3.

2. The phrase "managed context" is unfortunately close to .NET's term "managed 
code", and would likely lead to confusion for IronPython folks (and other 
programmers with .NET experience)

3. "manager" is an extremely generic term that is already used in a lot of 
different ways in various programming contexts

Switching to Greg's suggestion of "context guard" and "guarded context" as the 
terms would allow us to hit the reset button and start the documentation 
afresh without terminology confusion resulting from the evolution of PEP 343 
and its implementation and documentation.

I think context guard also works better in terms of guarding entry to and exit 
from the guarded context, whereas I always wanted to call those operations 
"set up" and "tear down" for context managers.

The current @contextfactory decorator could be renamed to @guardfactory to 
make it explicit that it results in a factory function for context guards.

Cheers,
Nick.

P.S. I think I can hear anguished howls coming from the offices of various 
book publishers around the world ;)


-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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