Issue with single line nested for loop in Python

Question

I have data that exports in a string

output = '012345678910abcdefghijkl'

cleaned_output = [output[index:index + 4] for index in range(0, len(output), 4)]
cleaned_output = [cleaned_output[i][item] for i in range(0, len(cleaned_output)) for item in range(0,len(cleaned_output[i]))]

Which returns:

['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '1', '0', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l']

However, I am looking to return the below, any ideas on where I am going wrong?

[['0', '1', '2', '3'], ['4', '5', '6', '7'], ['8', '9', '1', '0'], ['a', 'b', 'c', 'd'], ['e', 'f', 'g', 'h'], ['i', 'j', 'k', 'l']]

Answer 1

You should just split your input into chunks of 4 and then convert them directly to lists:

cleaned_output = [list(output[i:i+4]) for i in range(0, len(output), 4)]

Output:

[['0', '1', '2', '3'], ['4', '5', '6', '7'], ['8', '9', '1', '0'], ['a', 'b', 'c', 'd'], ['e', 'f', 'g', 'h'], ['i', 'j', 'k', 'l']]