CODEWITHSUNDEEP
pythonmerge
valenzio
valenzio

Reputation: 823

Merge two lists together

I have two lists in python:

L1=[[100, 1], [101, 2]]
L2=[[100, 3], [101, 4], [102, 5]]

and I want to merge them so I get:

L_merge=[[100, 4], [101, 6], [102, 5]]

It is important that the two lists might be not of the same size.

I was trying to use dictionaries but could not figure it out. I am happy to use numpy, pandas or any other tools to get that merger.

Upvotes: 3

Views: 516

Answers (3)

mkj
mkj

Reputation: 2811

L1=[[100, 1], [101, 2]]
L2=[[100, 3], [101, 4], [102, 5]]

d = {}
for a,b in L1+L2:
  d[a] = d.get(a,0) + b
L_merge = [[k,v] for k,v in d.items()]

print(L_merge)

Upvotes: 0

Moses Koledoye
Moses Koledoye

Reputation: 78536

You could use a collections.Counter on both lists and simply sum them:

from collections import Counter

L1 = [[100, 1], [101, 2]]
L2 = [[100, 3], [101, 4], [102, 5]]

L_merge = (Counter(dict(L1)) + Counter(dict(L2))).items()
print(list(L_merge))
# [(100, 4), (101, 6), (102, 5)]

Upvotes: 5

Jack Cooper
Jack Cooper

Reputation: 418

why not just use a for loop:

L_merge = L2
for i in len(L1):
    L_merge[i][-1] += L1[i][-1]

The one caveat is that this only works if L2 is the longer of the 2 lists

Upvotes: 0

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