robert wrote:
> I want to use a computation cache scheme like
>> o = CACHECOMPUTE complex-key-expr expensive-calc-expr
>> frequently and elegantly without writing complex-key-expr or expensive-calc-expr twice.
> So its ugly:
>> _=complex-key-expr; o=cache.get(_) or cache.setdefault(_,expensive-calc-expr)
>> Any ideas?
in Python 2.5:
cache = collections.defaultdict(lambda: expensive-calc-expr)
value = cache[complex-key-expr]
or, if expensive-calc-expr needs access to the key:
class mycache(dict):
def __missing__(self, key):
value = expensive-calc-expr(key)
self[key] = value
return value
cache = mycache()
value = cache[complex-key-expr]
or, if expensive-calc-expr needs access to more than just the key, or
you need to run this on more than just 2.5:
cache = {}
key = complex-key-expr
try:
value = cache[key]
except KeyError:
value = cache[key] = expensive-calc-expr
</F>
