Python: Merge an item from one list to two items another

Question

I am new to python, I am stuck, and I need help. Given a list as this:

listA = [1,2,3,4,5]
listB = [6,7,8,9,10,11,12,13,14,15]

I want to pick one Item from listA, Pick two Items from ListB, and have an output like this:

Item 1 from listA is joined with item 6 and 7 from listB

This should in a loop till there are no more items in listA

Thanks. all help appreciated.

score 0 · Answer 1 · answered Apr 30 '17 at 12:25

0

Here is the solution

listA = [1,2,3,4,5]
listB = [6,7,8,9,10,11,12,13,14,15]

j= 0
for i in listA:
    print ("Item %d from listA is joined with item %d and %d from listB")%(i,listB[j],listB[j+1])
    j+=2

answered Apr 30 '17 at 12:25

Nipun Garg

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hiro protagonist · Accepted Answer · 2017-04-30T12:41:39.803

you could try this:

listA = [1,2,3,4,5]
listB = [6,7,8,9,10,11,12,13,14,15]

for a, b1, b2 in zip(listA, listB[::2], listB[1::2]):
    print(('Item {} from listA is joined with item {} and {} '
           'from listB').format(a, b1, b2))

if you actually wanted to create a new list, merged in the way you described, this would work:

merged = [a for abc in zip(listA, listB[::2], listB[1::2]) for a in abc ]
print(merged)  # [1, 6, 7, 2, 8, 9, 3, 10, 11, 4, 12, 13, 5, 14, 15]

taking the things apart:

listB[::2]  # [6, 8, 10, 12, 14]  (every other element starting at 0)
listB[1::2]  # [7, 9, 11, 13, 15] (every other element starting at 1)
[abc for abc in zip(listA, listB[::2], listB[1::2])] # [(1, 6, 7), (2, 8, 9), ...

and then you just need to flatten that list.

oh, you do not actually want to merge the list that way, but print out that string... that could be done like this:

score 0 · Answer 3 · answered May 01 '17 at 08:32

listA = [1,2,3,4,5]
listB = [6,7,8,9,10,11,12,13,14,15]

start,end,step = 0 , 2 , 2
for itemA in listA:
  listB_item1,listB_item2 = listB[start:end]
  print('Item',itemA,'from listA is joined with item',listB_item1,'and',listB_item2,'from listB')
  start = start + step
  end = start + step

RESULT

Item 1 from listA is joined with item 6 and 7 from listB
Item 2 from listA is joined with item 8 and 9 from listB
Item 3 from listA is joined with item 10 and 11 from listB
Item 4 from listA is joined with item 12 and 13 from listB
Item 5 from listA is joined with item 14 and 15 from listB

Python: Merge an item from one list to two items another

3 Answers3