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Python program to interchange first and last elements in a list

  • Difficulty Level : Easy
  • Last Updated : 26 Jul, 2021

Given a list, write a Python program to swap first and last element of the list.

Examples: 

Input : [12, 35, 9, 56, 24]
Output : [24, 35, 9, 56, 12]

Input : [1, 2, 3]
Output : [3, 2, 1]

Approach #1: Find the length of the list and simply swap the first element with (n-1)th element.

Python3




# Python3 program to swap first
# and last element of a list
 
# Swap function
def swapList(newList):
    size = len(newList)
     
    # Swapping
    temp = newList[0]
    newList[0] = newList[size - 1]
    newList[size - 1] = temp
     
    return newList
     
# Driver code
newList = [12, 35, 9, 56, 24]
 
print(swapList(newList))

Output:

[24, 35, 9, 56, 12]

Approach #2: The last element of the list can be referred as list[-1]. Therefore, we can simply swap list[0] with list[-1].

Python3




# Python3 program to swap first
# and last element of a list
 
# Swap function
def swapList(newList):
     
    newList[0], newList[-1] = newList[-1], newList[0]
 
    return newList
     
# Driver code
newList = [12, 35, 9, 56, 24]
print(swapList(newList))

Output:

[24, 35, 9, 56, 12]

Approach #3: Swap the first and last element is using tuple variable. Store the first and last element as a pair in a tuple variable, say get, and unpack those elements with first and last element in that list. Now, the First and last values in that list are swapped. 

Python3




# Python3 program to swap first
# and last element of a list
 
# Swap function
def swapList(list):
     
    # Storing the first and last element
    # as a pair in a tuple variable get
    get = list[-1], list[0]
     
    # unpacking those elements
    list[0], list[-1] = get
     
    return list
     
# Driver code
newList = [12, 35, 9, 56, 24]
print(swapList(newList))

Output:

[24, 35, 9, 56, 12]

Approach #4: Using * operand. 
This operand proposes a change to iterable unpacking syntax, allowing to specify a “catch-all” name which will be assigned a list of all items not assigned to a “regular” name. 

Python3




# Python3 program to illustrate
# the usage of * operarnd
list = [1, 2, 3, 4]
 
a, *b, c = list
 
print(a)
print(b)
print(c)

Output: 

1
[2, 3]
4

Now let’s see the implementation of above approach: 

Python3




# Python3 program to swap first
# and last element of a list
 
# Swap function
def swapList(list):
     
    start, *middle, end = list
    list = [end, *middle, start]
     
    return list
     
# Driver code
newList = [12, 35, 9, 56, 24]
 
print(swapList(newList))

Output:

[24, 35, 9, 56, 12]

Approach #5: Swap the first and last elements is to use the inbuilt function list.pop(). Pop the first element and store it in a variable. Similarly, pop the last element and store it in another variable. Now insert the two popped element at each other’s original position. 

Python3




# Python3 program to swap first
# and last element of a list
 
# Swap function
def swapList(list):
     
    first = list.pop(0)  
    last = list.pop(-1)
     
    list.insert(0, last) 
    list.append(first)  
     
    return list
     
# Driver code
newList = [12, 35, 9, 56, 24]
 
print(swapList(newList))

Output: 

[24, 35, 9, 56, 12]

 


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