CODEWITHSUNDEEP
pythonlist
Kay
Kay

Reputation: 915

Python: Add value to a list at predefined indexes

I have a list (aList) I need to create another list of the same length as aList (checkColumn) and add 1 at the positions defined in the index list (indexList), the positions not defined in the indexList should be 0

Input:

aList = [70, 2, 4, 45, 7 , 55, 61, 45]
indexList = [0, 5, 1]

Desired Output: 

checkColumn = [1,1,0,0,0,1]

I have been experimenting around with the following code, but I get the output as [1,1]

for a in len(aList):
    if a == indexList[a]:
        checkColumn = checkColumn[:a] + [1] + checkColumn[a:]
    else:
        checkColumn = checkColumn[:a] + [0] + checkColumn[a:]

I have tried with checkColumn.insert(a, 1) and I get the same result. Thanks for the help!

Upvotes: 1

Views: 76

Answers (2)

Pranav Hundekari
Pranav Hundekari

Reputation: 56

Would this help?

First, you initialize checkColumn with 0

checkColumn = [0] * len(aList)

Then, loop through indexList and update the checkColumn

for idx in indexList:
    checkColumn[idx] = 1

Cheers!

Upvotes: 3

DavidG
DavidG

Reputation: 25362

You could do this in one line using a list comprehension:

aList = [70, 2, 4, 45, 7 , 55, 61, 45]
indexList = [0, 5, 1]

checkColumn = [1 if a in indexList else 0 for a in range(len(aList))]
print(checkColumn)
# [1, 1, 0, 0, 0, 1, 0, 0]

Upvotes: 2

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