How to mathematically subtract two lists in python?

Question

I know subtraction of lists is not supported in python, however there are some ways to omit the common elements between two lists. But what I want to do is subtraction of each element in one list individually with the corresponding element in another list and return the result as an output list. How can I do this?

     A = [3, 4, 6, 7]
     B = [1, 3, 6, 3]
     print A - B  #Should print [2, 1, 0, 4]

score 23 · Accepted Answer · edited May 23 '17 at 10:31

23

Use operator with map module:

>>> A = [3, 4, 6, 7]
>>> B = [1, 3, 6, 3]
>>> map(operator.sub, A, B)
[2, 1, 0, 4]

As @SethMMorton mentioned below, in Python 3, you need this instead

>>> A = [3, 4, 6, 7]
>>> B = [1, 3, 6, 3]
>>> list(map(operator.sub, A, B))
[2, 1, 0, 4]

Because, map in Python returns an iterator instead.

edited May 23 '17 at 10:31

Community

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answered Apr 19 '14 at 17:41

Thanakron Tandavas

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Watch out, on python 3 this does not return a `list`, but a *map object*. You need `list(map(operator.sub, A, B))` to get the same result. – SethMMorton Apr 19 '14 at 18:53
@SethMMorton nice catch. I will add that to the answer – Thanakron Tandavas Apr 19 '14 at 19:44

score 13 · Answer 2 · answered Apr 19 '14 at 17:38

13

You can use zip and a list comprehension:

>>> A = [3, 4, 6, 7]
>>> B = [1, 3, 6, 3]
>>> zip(A, B) # Just to demonstrate
[(3, 1), (4, 3), (6, 6), (7, 3)]
>>> [x - y for x, y in zip(A, B)]
[2, 1, 0, 4]
>>>

answered Apr 19 '14 at 17:38

score 0 · Answer 3 · answered Apr 19 '14 at 17:41

0

Try something like

def substract_lists(a, b):
    for i, val in enumerate(a):
            val = val - b[i]
    return a

answered Apr 19 '14 at 17:41

Lucas S.

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How to mathematically subtract two lists in python?

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