[Python-ideas] Automatic context managers

[David Mertz]

On Apr 26, 2013, at 12:46 PM, Bruce Leban wrote:
> On Fri, Apr 26, 2013 at 12:37 PM, David Mertz <mertz at gnosis.cx> wrote:
> I'd note that there's no reason you couldn't use the so-called "automatic context manager" already, it's just a matter of writing your own function rather than the built-in 'open()'.  So, e.g. with a few lines of definition, you might use:
> 
>   boolean = SafeOpen(resource).use()
> 
> I'd like to see those few lines if they are indeed possible. I don't see how the function would know when to call __exit__. It has to be after use() finishes.

You might get really perverse with stack inspection and whatnot.  But I was thinking more of just a proxy method that introduced the safety.

class SafeOpen(object):
    def __init__(self, resource):
        self.resource = resource
    def __getattr__(self, name):
        def f(*args, **kws):
            with open(self.resource) as x:
                y = getattr(x, name)(*args, **kws)
            return y
        return f





--
If I seem shortsighted to you, it is only because I have stood on the backs of midgets.