CODEWITHSUNDEEP
pythonlistpython-3.x
ᴘᴀɴᴀʏɪᴏᴛɪs
ᴘᴀɴᴀʏɪᴏᴛɪs

Reputation: 7529

Adding items from pairs in list of lists

How can I zip pairs in a list-of-lists?

 A=[[ 1,2 ],[ 3  ,  4]]
 B=[[ 4,5 ],[ 8  ,  9]]
 ->(1,4),(2,5),(3,8),(4,9)

I've tried something like zip(*A,*B) but I'm getting SyntaxError: only named arguments may follow *expression.

In the end what I'm trying to do is add them:

 A=[[ 1,2 ],[ 3  ,  4]]
 B=[[ 4,5 ],[ 8  ,  9]]
  =[[ 5,7 ],[ 11 , 13]]

(also doesn't work):

add= [i+j for i,j in zip(*A,*B)]

Upvotes: 1

Views: 45

Answers (2)

falsetru
falsetru

Reputation: 369324

Consider using numpy:

>>> A = [[1, 2], [3, 4]]
>>> B = [[4, 5], [8, 9]]
>>> import numpy
>>> numpy.array(A) + numpy.array(B)
array([[ 5,  7],
       [11, 13]])

>>> list(map(list, _))
[[5, 7], [11, 13]]

Upvotes: 0

thefourtheye
thefourtheye

Reputation: 239593

First, zip both A and B and then zip the lists given by the previous zip, like this

result = []
for items in zip(A, B):
    for data in zip(*items):
        result.append(data)

The same can be written succinctly as a List Comprehension, like this

>>> [data for items in zip(A, B) for data in zip(*items)]
[(1, 4), (2, 5), (3, 8), (4, 9)]

Upvotes: 2

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