Python program to interchange first and last elements in a list
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 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)) |
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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 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)) |
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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 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)) |
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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 program to illustrate # the usage of * operarnd list = [1, 2, 3, 4] a, *b, c = list print(a) print(b) print(c) |
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Output:
1 [2, 3] 4
Now let’s see the implementation of above approach:
# 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)) |
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Output:
[24, 35, 9, 56, 12]
Approach #5: Swap the first and last elements is to use inbuilt function list.pop(). Pop the first element and store it in a variable. Similarily pop the last element and store it in another variable. Now insert the two popped element at each other’s original position.
# 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)) |
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Output:
[24, 35, 9, 56, 12]
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