Lists of lists traversal

[Kaleissin]

In article <83m3fn$sb6$1 at cronkite.cc.uga.edu>, Benjamin Dixon wrote:
>Hello, I am new to Python and am trying to figure out how I can iterate
>over a list that I know to contain other lists of integers so that I can
>add up the individual lists inside the larger list.
>
>I tried things like this:
>
>Sum(input):
>	for x in input:
>		value = 0
>		for y in input:
>			value = value + y
>	return y
>
>and other stuff but I'm not certain as to how to reference a specific
>member of a given sublist.

If I understand you correctly... you want to 'compress' the inner lists 
and replace them with their sums?

If that is the case... 

Summing a list:

result = reduce(lambda x, y: x+y, list_to_sum)

What I would do in your case:

listpos = 0
while listpos < len(list_of_lists):
	list_of_lists[listpos] = reduce(lambda x, y: x+y, list_of_lists[listpos])
	listpos = listpos + 1

This destroys the original lists btw. To keep them, append the resulting 
sum to some other list instead of replacing the list with it as above. 
You could use a for instead of the while too, in that case.

It might not be very effective but it looks nice... list comprehension 
version, anyone?


kal.
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