Refactoring; arbitrary expression in lists
jeff at ccvcorp.com
Thu Jan 13 13:22:28 EST 2005
Stephen Thorne wrote:
> As for the overall efficiency concerns, I feel that talking about any
> of this is premature optimisation.
I disagree -- using REs is adding unnecessary complication and
dependency. Premature optimization is a matter of using a
conceptually more-complicated method when a simpler one would do; REs
are, in fairly simple cases such as this, clearly *not* simpler than
> The optimisation that is really
> required in this situation is the same as with any
> large-switch-statement idiom, be it C or Python. First one must do a
> frequency analysis of the inputs to the switch statement in order to
> discover the optimal order of tests!
But if you're using a dictionary lookup, then the frequency of inputs
is irrelevant. Regardless of the value of the input, you're doing a
single hash-compute and (barring hash collisions) a single
bucket-lookup. Since dicts are unordered, the ordering of the literal
(or of a set of statements adding to the dict) doesn't matter.
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