CODEWITHSUNDEEP
pythonlist
user3844491
user3844491

Reputation: 21

Python: how to add first value in each list

A Posn is a list of length two [x,y], where x and y are both Float values, corresponding to the x and y coordinates of the point, respectively.

 make_posn: float float -> Posn
def make_posn(x_coord, y_coord):
    return [x_coord, y_coord]

How do I add all the x-values in a list of Posns?

Ex: [ [3.0, 4.0], [8.0, -1.0], [0.0, 2.0]] would be 11

Upvotes: 0

Views: 99

Answers (2)

user1907906
user1907906

Reputation:

sum them:

In [2]: sum(x[0] for x in [ [3.0, 4.0], [8.0, -1.0], [0.0, 2.0]])
Out[2]: 11.0

Upvotes: 2

Paris
Paris

Reputation: 6771

The following piece of code should work for your

_sum = 0.0
for sublist in [ [3.0, 4.0], [8.0, -1.0], [0.0, 2.0]]:
    _sum += sublist[0]

It initializes a sum accumulator to zero and then iterates over the sublist elements of the list to add the value of the first element of each list, to the initial sum

Upvotes: 0

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