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Python program to Swap i’th with j’th elements in List

  • Last Updated : 13 Jan, 2021

Given a list, the task is to write a Python program to the given list of elements, toggle every i and j elements in the list.

Examples:

Input : test_list = [4, 7, 8, 0, 8, 4, 2, 9, 4, 8, 4], i, j = 4, 8 
Output : [8, 7, 4, 0, 4, 8, 2, 9, 8, 4, 8] 
Explanation : 4 is swapped by 8 at each occurrence.

Input : test_list = [4, 7, 8, 0, 8, 4], i, j = 4, 8 
Output : [8, 7, 4, 0, 4, 8] 
Explanation : 4 is swapped by 8 at each occurrence. 
 

Method 1: Using loop + conditional statements



In this, we perform the task of toggling using conditional if-else statements, and the task of iteration is performed using a loop.

Python3




# Python3 code to demonstrate working of
# Toggle i,j elements in List
# Using loop + conditional statements
  
# initializing list
test_list = [4, 7, 8, 0, 8, 4, 2, 9, 4, 8, 4]
               
# printing original list
print("The original list is : " + str(test_list))
  
# initializing i, j 
i, j = 4, 8
  
for idx in range(len(test_list)):
      
    # perform toggling
    if int(test_list[idx]) == i:
        test_list[idx] = j
    elif int(test_list[idx]) == j:
        test_list[idx] = i
          
# printing result
print("The altered list : " + str(test_list))

Output:

The original list is : [4, 7, 8, 0, 8, 4, 2, 9, 4, 8, 4]
The altered list : [8, 7, 4, 0, 4, 8, 2, 9, 8, 4, 8]

Method 2: Using list comprehension + external function

In this, we perform the task of toggling using the external toggle function, and list comprehension is used to iterate through the list.

Python3




# Python3 code to demonstrate working of
# Toggle i,j elements in List
# Using list comprehension + external function
  
# external toggle 
def toggle(ele, i, j):
  
    # performing toggle
    if ele == i:
        return j
    elif ele == j:
        return i
    return ele
  
# initializing list
test_list = [4, 7, 8, 0, 8, 4, 2, 9, 4, 8, 4]
               
# printing original list
print("The original list is : " + str(test_list))
  
# initializing i, j 
i, j = 4, 8
  
# list comprehension for 1 liner
res = [toggle(ele, i, j) for ele in test_list]
          
# printing result
print("The altered list : " + str(res))

Output:

The original list is : [4, 7, 8, 0, 8, 4, 2, 9, 4, 8, 4]
The altered list : [8, 7, 4, 0, 4, 8, 2, 9, 8, 4, 8]

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