Python program to interchange first and last elements in a list

In this article, we will learn how to interchange the first and last elements in a Python list. This is a common programming task with multiple implementation approaches.

Problem statement − We are given a list, and we need to swap the first element with the last element.

There are 4 approaches to solve this problem as discussed below −

Using Temporary Variable

The most straightforward approach uses a temporary variable to hold one element during the swap operation ?

def swapLast(data_list):
    size = len(data_list)
    # Swap operation using temporary variable
    temp = data_list[0]
    data_list[0] = data_list[size - 1]
    data_list[size - 1] = temp
    return data_list

# Driver code
data_list = ['t', 'u', 't', 'o', 'r', 'i', 'a', 'l']
print("Original list:", data_list)
result = swapLast(data_list)
print("After swapping:", result)

Original list: ['t', 'u', 't', 'o', 'r', 'i', 'a', 'l']
After swapping: ['l', 'u', 't', 'o', 'r', 'i', 'a', 't']

Using Negative Indexing

This approach is similar to the first one but uses Python's negative indexing to access the last element ?

def swapLast(data_list):
    # Swap operation using negative indexing
    temp = data_list[0]
    data_list[0] = data_list[-1]
    data_list[-1] = temp
    return data_list

# Driver code
data_list = ['t', 'u', 't', 'o', 'r', 'i', 'a', 'l']
print("Original list:", data_list)
result = swapLast(data_list)
print("After swapping:", result)

Original list: ['t', 'u', 't', 'o', 'r', 'i', 'a', 'l']
After swapping: ['l', 'u', 't', 'o', 'r', 'i', 'a', 't']

Using Tuple Packing and Unpacking

Python allows simultaneous assignment using tuple packing and unpacking, making the swap operation more concise ?

def swapLast(data_list):
    # Packing the elements into a tuple
    get = data_list[-1], data_list[0]
    # Unpacking those elements
    data_list[0], data_list[-1] = get
    return data_list

# Driver code
data_list = ['t', 'u', 't', 'o', 'r', 'i', 'a', 'l']
print("Original list:", data_list)
result = swapLast(data_list)
print("After swapping:", result)

Original list: ['t', 'u', 't', 'o', 'r', 'i', 'a', 'l']
After swapping: ['l', 'u', 't', 'o', 'r', 'i', 'a', 't']

Using Extended Unpacking

This approach uses Python's extended unpacking syntax with the * operator to separate the first, middle, and last elements ?

def swapLast(data_list):
    # Unpacking first, middle elements, and last
    start, *middle, end = data_list
    # Reconstructing with swapped positions
    data_list = [end, *middle, start]
    return data_list

# Driver code
data_list = ['t', 'u', 't', 'o', 'r', 'i', 'a', 'l']
print("Original list:", data_list)
result = swapLast(data_list)
print("After swapping:", result)

Original list: ['t', 'u', 't', 'o', 'r', 'i', 'a', 'l']
After swapping: ['l', 'u', 't', 'o', 'r', 'i', 'a', 't']

Comparison

Conclusion

All four methods effectively swap the first and last elements in a list. The tuple packing approach is most Pythonic, while the temporary variable method is clearest for beginners.