Subtracting Elements of a Sublist in Python 3

[pangloss3030]

Hello,

I am having an issue with subtracting sublists. With the given sublist:

first_list: [[0, 1], [2,4], [8,7]]

There is supposed to be a new list where that contains the difference of the first element from the second element in the sublist:

[-1,-2,-1]

This is the code so far:

for sub_list in data:
differences.append((int(sub_list[1]))-(int(sub_list[0])) in data)

I tried to run this with the other part of the problem to multiply the resulting list, but it fails. It seems to be not iterating. Can anyone offer some suggestions?

[DeaD_EyE]

from functools import reduce
import operator


# naive way
def sub_list(iterable):
    result = []
    for sub_list in iterable:
        result.append(sub_list[0] - sub_list[1])
    return result

# as list comprehension
def sub_list2(iterable):
    return [sub_list[0] - sub_list[1] for sub_list in iterable]


# with reduce and operator
def sub_list3(iterable):
    return [reduce(operator.sub, sub_list) for sub_list in iterable]


first_list = [[0, 1], [2,4], [8,7]]

The last function allows to have more than two elements in the sublist.

[pangloss3030]

Thank you for getting back to me.

[buran]

note that your expected output is incorrect and not consistent with your attempt at code
elements with index 0 and 1 are calculated as 0-1 and 2-4, while element with index 2 is calculated as 7-8
in your attempt you do int(sub_list[1])-int(sub_list[0]), so basically if that's correct the output is [1, 2, -1]

>>> spam = [[0, 1], [2,4], [8,7]]
>>> [n2-n1 for n1, n2 in spam]
[1, 2, -1]