On 19/11/2019 17:50, Soni L. wrote:
On 2019-11-19 3:37 p.m., Rhodri James wrote:
On 19/11/2019 17:12, Brian Skinn wrote:
@jayvdb on GitHub and I are working on a new version of one of my
packages, stdio-mgr (https://github.com/bskinn/stdio-mgr), with a
dramatically expanded API and capabilities.
Context managers feature heavily in the planned design; part of the
design plan is to allow instantiation of a StdioManager object prior
to entering a context, so that the user can tweak settings on the
resulting object beforehand:
cm = StdioManager()
cm.setting = True
cm.other_setting = False
with cm:
{do stuff with stdio managed}
If this paradigm holds, we will *specifically* be exploiting the
distinction between __init__ and __enter__.
-42 to abolishing __enter__.
I concur. Logically the problem that people are complaining about is
that we use open() as the context manager rather than a class that
defers the actual file open to __enter__(). That's fixable by writing
your own wrapper class, but having a builtin file context manager that
deferred resource-consuming actions would be a Good Thing™
How about using Paths as file context managers? Just an idle thought.
I still feel like opening the file but delaying the exception would be
more beneficial and have better semantics. It allows cd, mv, rm, etc to
happen without any surprising semantics, and fits the model you want it
to fit.
It really doesn't.
In my experience, lying to the user (or the compiler, or whatever) is
very rarely a good idea. Either the file is open or it isn't, and
finding out half a mile of text away from where the error actually
occurred that it isn't doesn't give you much opportunity to fix things.
As to the expected semantics of cd, mv, rm etc, I wouldn't expect those
to work on an open file at all, and I wouldn't be sure what happened if
they did.
--
Rhodri James *-* Kynesim Ltd
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