[Tutor] range efficiency

[Prasad, Ramit]

Jim Mooney wrote:
> If I'm using a variable-dependent range in a for loop, is Python smart
> enough to figure the variable once so I don't have to hoist it up?
> 
> That is for c in range(0,x+2), is x+2 figured once or every time
> through the loop? I'm assuming it's once but I like to verify.
> 
> I'll figure this myself once I get an editor I like with a profiler,
> but I'm still trying editors and don't want to spend all my time on
> them. So far I'm in between too simple, overkill, or buggy. And I
> don't want anything that uses Java. I'm allergic to Java ;')
> 
> --
> Jim Mooney
> 
> "For anything that matters, the timing is never quite right, the
> resources are always a little short, and the people who affect the
> outcome are always ambivalent."

x+2 is only calculated once and then passed to range. The for loop
then iterates over the range object. It is not recreating/re-calling
range(). 

Note in python 2 you should use xrange as it is a generator and 1. lazy 
2. more memory efficient. Unlike Python 2, in Python 3 range is a 
generator.


~Ramit




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