On Sun, 17 Apr 2011 19:07:03 +1000, Chris Angelico wrote: > If there's the > possibility of _ANY_ value coming back from the computation, then it > would need to be done as: > > if x in cache: return cache[x]
Or you can create a sentinel value that is guaranteed to never appear anywhere else: SENTINEL = object() obj = cache.get(x, SENTINEL) if obj is SENTINEL: obj = calculate(x) cache[x] = obj return obj You can create the sentinel once, at the start of your program, rather than each time. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
