Chris Angelico rosuav at gmail.com
Mon Mar 21 20:15:49 EDT 2016

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On Tue, Mar 22, 2016 at 11:05 AM, Steven D'Aprano <steve at 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

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