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Python program to swap any two elements in the list

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mahmoud2506
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2022-05-22
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Python program to swap two elements in a list using the index

We will take a list and two indexes (for swapping ) from the user and then swap the values at the given index in the list.

Example:

Sample Input:
[3, 1, 0, 9, 23, 89, 10] , 2, 5

Output:
[3, 1, 89, 9, 23, 0, 10]
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mahmoud2506
2022-05-22
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Method 1: Simply swap values using comma separator

We will swap the elements directly using the common swapping method.

Syntax:

a, b = b, a

Program to swap any two elements in the list

# Python program to swap element of a list

# Getting list from user
myList = []
length = int(input("Enter number of elements: "))
for i in range(0, length):
    val = int(input())
    myList.append(val)

print("Enter indexes to be swapped ")
index1 = int(input("index 1: "))
index2 = int(input("index 2: "))

print("Initial List: ", myList)
# Swapping given elements
myList[index1], myList[index2] = myList[index2], myList[index1]

# Printing list 
print("List after Swapping: ", myList)

Output:

Enter number of elements: 5
10
20
30
40
50
Enter indexes to be swapped
index 1: 2
index 2: 4
Initial List:  [10, 20, 30, 40, 50]
List after Swapping:  [10, 20, 50, 40, 30]

Method 2: Pop values and then inserting them back

One more method to swap values is to pop out values at a given index and then insert them back to the given index.

Algorithm :

  • Get list and index values from the user.
  • Swap values using pop and insert method.
    • val1 = pop(index1)
    • val2 = pop(index2 - 1)
    • insert(index1, val2)
    • insert(index2, val1)
  • Print the list.

Program to swap any two elements in the list

# Python program to swap element of a list

# Getting list from user
myList = []

length = int(input("Enter number of elements  "))
for i in range(0, length):
    val = int(input())
    myList.append(val)

print("Enter indexes to be swapped ")
index1 = int(input("index 1: "))
index2 = int(input("index 2: "))

print("Initial List: ", myList)
# Swapping given element
val1 = myList.pop(index1)
val2 = myList.pop(index2 - 1)
myList.insert(index1, val2)
myList.insert(index2, val1)

# Printing list 
print("List after Swapping: ", myList)

Output:

Enter number of elements  5
10
20
30
40
50
Enter indexes to be swapped
index 1: 1
index 2: 4
Initial List:  [10, 20, 30, 40, 50]
List after Swapping:  [10, 50, 30, 40, 20]

Swapping two values based on their values entered by the user

# Python program to swap element of a list

# Getting list from user
myList = []
length = int(input("Enter number of elements: "))
for i in range(0, length):
    val = int(input())
    myList.append(val)

print("Enter values to be swapped ")
value1 = int(input("value 1: "))
value2 = int(input("value 2: "))

index1 = myList.index(value1)
index2 = myList.index(value2)

print("Initial List: ", myList)

# Swapping given element
myList[index1], myList[index2] = myList[index2], myList[index1]

# Printing list 
print("List after Swapping: ", myList)

Output:

Enter number of elements: 5
10
20
30
40
50
Enter values to be swapped
value 1: 10
value 2: 50
Initial List:  [10, 20, 30, 40, 50]
List after Swapping:  [50, 20, 30, 40, 10]

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