substituting list comprehensions for map()

[Steven D'Aprano]

On Sun, 01 Nov 2009 23:54:16 -0800, Jon P. wrote:

> I'd like to do:
> 
> resultlist = operandlist1 + operandlist2
> 
> where for example
> 
> operandlist1=[1,2,3,4,5]
> operandlist2=[5,4,3,2,1]
> 
> and resultlist will become [6,6,6,6,6].  Using map(), I can do:
> 
> map(lambda op1,op2: op1 + op2, operandlist1, operandlist2)


If the two lists are very large, it would be faster to use this:


from operator import add
map(add, operandlist1, operandlist2)


> Is there any reasonable way to do this via a list comprehension ?

[x+y for (x, y) in zip(operandlist1, operandlist2)]

If the lists are huge, you can save some temporary memory by replacing 
zip with itertools.izip.




-- 
Steven