Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: Chris Angelico <rosuav@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: Static caching property
Date: Tue, 22 Mar 2016 11:15:49 +1100
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On Tue, Mar 22, 2016 at 11:05 AM, Steven D'Aprano <steve@pearwood.info> wrote:
> But my favourite is to combine them:
>
>
> class Desc:
>     def __get__(self, obj, type):
>         sentinel = object()  # guaranteed to be unique
>         value = getattr(type, _cached_value, sentinel)
>         if value is sentinel:
>             value = type._cached_value = compute_value(type)
>         return value
>
>
>

That seems like overkill. Inside getattr is the equivalent of:

try: return type._cached_value
except AttributeError: return sentinel

So skip getattr/hasattr and just use try/except:

class Desc:
    def __get__(self, obj, type):
        try:
            return type._cached_value
        except AttributeError:
            value = type._cached_value = compute_value(type)
            return value

ChrisA