Speed-up for loops

Roy Smith roy at panix.com
Tue Sep 7 14:09:12 CEST 2010

In article <ny3ho.32445$la2.18202 at newsfe23.ams2>,
 "BartC" <bartc at freeuk.com> wrote:

> (BTW why doesn't Python 3 just accept 'xrange' as a 
> synonym for 'range'?)

If you've ever tried to maintain a legacy code base, you'll understand 
why "there's only one way to do it" is A Good Thing.

Imagine that you're looking at some code which was written years ago, by 
people who are no longer around to answer questions.  In one place, you 

for i in range(n):

and in another, you see:

for j in xrange(n):

If you are truly a Python expert, you'll say to yourself, "range and 
xrange are synonyms", and move on to other things.  If, however, you're 
not really an expert, you'll look at this and say, "Hmmm, in one place 
they used range(), and in another they used xrange().  Clearly, there's 
some reason for the difference, I need to figure out what it is, because 
that's probably key to my understanding why this code isn't working".  
So, you spend the next two hours pouring over reference manuals trying 
to understand the subtle difference, until your friend comes over and 
says, "You dolt, you just wasted half the afternoon.  They're the same 
thing.  Move on, this is not the bug you're looking for".

If you think stuff like that can't happen, you've probably never jumped 
into the middle of a legacy code base written in a language you don't 
know very well.

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