Python | Split a list into sublists of given lengths

The problem of splitting a list into sublists is quite generic but to split in sublist of given length is not so common. Given a list of lists and list of length, the task is to split the list into sublists of given length. Example: 

Input : Input = [1, 2, 3, 4, 5, 6, 7]
        length_to_split = [2, 1, 3, 1]

Output: [[1, 2], [3], [4, 5, 6], [7]]

Method #1: Using islice to split a list into sublists of given length, is the most elegant way. 

Python3

# Python code to split a list
# into sublists of given length.

from itertools import islice

# Input list initialization
Input = [1, 2, 3, 4, 5, 6, 7]

# list of length in which we have to split
length_to_split = [2, 1, 3, 1]

# Using islice
Inputt = iter(Input)
Output = [list(islice(Inputt, elem))
        for elem in length_to_split]

# Printing Output
print("Initial list is:", Input)
print("Split length list: ", length_to_split)
print("List after splitting", Output)

Output:

Initial list is: [1, 2, 3, 4, 5, 6, 7]
Split length list:  [2, 1, 3, 1]
List after splitting [[1, 2], [3], [4, 5, 6], [7]]

Time Complexity: O(n)
Auxiliary Space: O(1)

Method #2: Using zip is another way to split a list into sublists of given length. 

Python3

# Python code to split a list into
# sublists of given length.
from itertools import accumulate

# Input list initialization
Input = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

# list of length in which we have to split
length_to_split = [2, 2, 3, 3]

# Using islice
Output = [Input[x - y: x] for x, y in zip(
        accumulate(length_to_split), length_to_split)]

# Printing Output
print("Initial list is:", Input)
print("Split length list: ", length_to_split)
print("List after splitting", Output)

Output:

Initial list is: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Split length list:  [2, 2, 3, 3]
List after splitting [[1, 2], [3, 4], [5, 6, 7], [8, 9, 10]]

Time Complexity: O(1)

Auxiliary Space: O(1)