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Python | Combine the first and last items separately in a list

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Examples :

  Input:  [[’x’,’ y’], [’a’,’ b’], [ ’m’,’ n’]]  Output:  [[’x’,’ a’, ’m’], [’ y’, ’b’,’ n’]]  Input:  [[1, 2], [3, 4], [5, 6], [7, 8]]  Output:  [[1, 3, 5, 7] , [2, 4, 6, 8]] 

Approach # 1: list comprehension and zip

# Python3 program for merging the first and the last
# elements separately in the list of lists

 

def merge (lst):

 

return [ list (ele) for ele in list ( zip ( * lst) )]

 
# Driver code

lst = [[ ’x’ , ’ y’ ], [ ’a’ , ’ b’ ], [ ’m’ , ’ n’ ]]

print (merge (lst))

Exit:

 [[’x ’,’ a’, ’m’], [’ y’, ’b’,’ n’]] 
Approach # 2 Using the Numpy

array

First convert the given list to a numpy array and then return the transpose of the array and finally convert the array to a list.

# Python3 program to merge first and last
# elements separately in the list of lists

import numpy as np

 

def merge (lst):

arr = np.array (lst)

return arr.T.tolist ()

 
# Driver code

lst = [[ ’x’ , ’y’ ], [ ’ a’ , ’b’ ], [ ’ m’ , ’n’ ]]

print (merge (lst))

Exit:

 [[’x’,’ a’, ’m’], [’ y’, ’b’,’ n ’]] 

Python | Combine the first and last items separately in a list NumPy: Questions

Python | Combine the first and last items separately in a list Python functions: Questions

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