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
def swapList[newList]:
size = len[newList]
temp = newList[0]
newList[0] =
newList[size - 1]
newList[size - 1] = temp
return newList
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
def swapList[newList]:
newList[0], newList[-1] = newList[-1], newList[0]
return newList
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
def swapList[list]:
get = list[-1], list[0]
list[0], list[-1] = get
return
list
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
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
def swapList[list]:
start, *middle, end = list
list =
[end, *middle, start]
return list
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
def swapList[list]:
first = list.pop[0]
last = list.pop[-1]
list.insert[0, last]
list.append[first]
return list
newList =
[12, 35, 9, 56, 24]
print[swapList[newList]]
Output:
[24, 35, 9, 56, 12]