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Python | Ways to join pair of elements in list

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Given a list, the task is to join a pair of elements of the list. Given below are a few methods to solve the given task.

Method #1: Using zip() method 

Python3




# Python code to demonstrate
# how to join pair of elements of list
 
# Initialising list
ini_list = ['a', 'b', 'c', 'd', 'e', 'f']
 
# Printing initial list
print ("Initial list", str(ini_list))
 
# Pairing the elements of lists
res = [i + j for i, j in zip(ini_list[::2], ini_list[1::2])]
 
# Printing final result
print ("Result", str(res))


Output:

Initial list ['a', 'b', 'c', 'd', 'e', 'f']
Result ['ab', 'cd', 'ef']

Time complexity: O(n), where n is the length of the initial list. 
Auxiliary space: O(n), as the final result list (res) is created and stored in memory, with a size proportional to the input list.

 Method #2: Using list comprehension and next and iters 

Python3




# Python code to demonstrate
# how to join pair of elements of list
 
# Initialising list
ini_list = iter(['a', 'b', 'c', 'd', 'e', 'f'])
 
# Pairing the elements of lists
res = [h + next(ini_list, '') for h in ini_list]
 
# Printing final result
print ("Result", str(res))


Output:

Result ['ab', 'cd', 'ef']

Time complexity: O(n)
Auxiliary space: O(n) 

Method #3: Using list comprehension 

Python3




# Python code to demonstrate
# how to join pair of elements of list
 
# Initialising list
ini_list = ['a', 'b', 'c', 'd', 'e', 'f']
 
# Printing initial lists
print ("Initial list", str(ini_list))
 
# Pairing the elements of lists
res = [ini_list[i] + ini_list[i + 1]
       for i in range(0, len(ini_list), 2)]
 
# Printing final result
print ("Result", str(res))


Output:

Initial list ['a', 'b', 'c', 'd', 'e', 'f']
Result ['ab', 'cd', 'ef']

Time Complexity: O(n) where n is the number of elements in the list “ini_list”.  
Auxiliary Space: O(n), where n is the number of elements in the new res list 



Last Updated : 24 Mar, 2023
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