如何在 Python 3 中减去嵌套列表中的元素？

Question

I have a nested list(the sublists will only have 2 elements), like this:

list_1 = [[1,2],[3,2]]

I want to subtract the elements inside each nested list, like this should be the output:

[-1,1]

To sum the numerals in the nested list, I only had to use:

list_1 = [[1,2],[3,2]]
store = []
for x in list_1:
    store.append(sum(x))

but in subtracting since I couldn't any function like 'sum' for subtracting on the internet, I tried create one like this:

list_1 = [[1,2],[3,2]]
store = []
def subtraction(z,l):
    total = z - l
    return total
for y in list_1:
    store.append(subtraction(y))

but it returned:

TypeError: subtraction() missing 1 required positional argument: 'l'

How can I get over this error and also make my code work?

Answer 1

You can use Extended Iterable Unpacking operator.

list_1 = [[1,2],[3,2]]
store = []
def subtraction(z,l):
    total = z - l
    return total
for y in list_1:
    store.append(subtraction(*y))

Another way is to use list comprehension .

list = [a-b for a, b in list]

Answer 2

您可以通过使用列表理解来实现这一点

store = [ l1-l2 for l1, l2 in list_1]

Answer 3

The way I would go about it is:

list_1 = [[1,2],[3,2]]
store = []
for a, b in list_1:
    store.append(a - b)

Answer 4

You can use a combination of map and lambda :

list(map(lambda x: x[0] - x[1], list_1))

Demo :

>>> list_1 = [[1,2],[3,2]]
>>> list(map(lambda x: x[0] - x[1], list_1))
[-1, 1]