[Python-Dev] lazy evaluation redux (was dict "setdefault". Feaure request or bugfix?)

[Jesus Cea Avion]

> One way to satisfy this would be to redefine setdefault something like
> this:
> 
> def setdefault(aDict, aKey, aValue=None, lazy=None):
>    assert aValue is None or lazy is None
>    if aKey not in aDict:
>        aDict[aKey] = (if lazy is None: aValue else: lazy())
>    return aDict[aKey]

Nice. Nevertheless I keep thinking that current "setdefault" behaviour
is not fully documented and counterintuitive :-). So we would need to
fix the behaviour or update docs :-p

God, you all mutate a fairly simple and concrete consideration into a
broad language "lazy evaluation" feature. I'm overhelmed };-)

>    myDict.setdefault(myKey, lazy=lambda:expensive_function(args))

Nice lambda usage: declare a pseudofunction that calls another function
with predefined parameters. Updating my toolbox... :)

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