Python | Convert 1D list to 2D list of variable length

Given a 1D list ‘lst’ and list of variable lengths ‘var_lst’, write a Python program to convert the given 1D list to 2D list of given variable lengths.

Examples:

Input : lst = [1, 2, 3, 4, 5, 6]
        var_lst = [1, 2, 3]
Output : [[1], [2, 3], [4, 5, 6]]

Input : lst = ['a', 'b', 'c', 'd', 'e']
        var_lst = [3, 2]
Output : [['a', 'b', 'c'], ['d', 'e']]

 
Method #1 : List slicing

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# Python3 program to Convert 1D 
# list to 2D list
from itertools import islice
  
def convert(lst, var_lst):
    idx = 0
    for var_len in var_lst:
        yield lst[idx : idx + var_len]
        idx += var_len
      
# Driver code
lst = [1, 2, 3, 4, 5, 6]
var_lst = [1, 2, 3]
print(list(convert(lst, var_lst)))

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Output:

[[1], [2, 3], [4, 5, 6]]

 
Method #2 : Using itertools.islice()

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# Python3 program to Convert 1D 
# list to 2D list
from itertools import islice
  
def convert(lst, var_lst):
    it = iter(lst)
    return [list(islice(it, i)) for i in var_lst]
      
# Driver code
lst = [1, 2, 3, 4, 5, 6]
var_lst = [1, 2, 3]
print(convert(lst, var_lst))

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Output:

[[1], [2, 3], [4, 5, 6]]


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