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My question is based on an earlier question and I can't find to figure out (nor find) the subsequent step I need.

Say I do have the same list of tuples, namely:

[(0, 1), (2, 3), (5, 7), (2, 1)]

Also I wish to find the sum of the first values in each pair, which could be done by the simple pythonic:

sum([pair[0] for pair in list_of_pairs])

as provided by David Z. However, in my case I only wish to sum from the first first value up until a following first value, say the first value at index N = 2. Thus, only calculate the sum of:

0 + 2 + 5

I have been trying things like:

sum([pair[0] for pair in list_of_pairs[:N])

but without success. Can anyone provide me with an elegant solution?

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Steyn W.
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1 Answers1

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you were very close to the solution

This works for me :

N=2

sum([pair[0] for pair in list_of_pairs[0:N+1]])

If you wants from middle then you can do this :

N=3
M=1
print sum([pair[0] for pair in list_of_pairs[M:N+1]])
Sachin Gupta
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