[Tutor] Working with lists

[btkuhn at email.unc.edu]

Hi everyone,

I seem to use this pattern alot when writing functions and I'm 
wondering if there is a more efficient method. It comes up whenever I 
want to work with more than one item in a list; for instance, say I 
want to add each consecutive number in alist and output the new list. 
Ideally, I'd be able to write:

for num in list1:
newlist.append(num+nextnum)

This doesn't work, though because there's no way to access "nextnum" 
unless I implement a "count" variable like this:

count=1
for num in list1:
newlist.append(num+list1[count])
count+=1

Instead, it usually ends up easier to write:

for index in range (len(list1)-1):
newlist.append((list1[index]+list1[index+1]))

It's not a big deal to have to write the additional code, but problems 
arise when I use this structure in the context of more complex 
functions, when I am passing multiple lists of varying length, because 
it is easy to get confused with the index numbers and I can't do 
anything to the last value of the list, since I then get an 
"indexerror" because the function tries to call "list[i+1]".

Is there a simpler way to do a procedure like this?

Thanks.