Python function: Check descending sort & empty list

Last update on January 06 2025 13:36:15 (UTC/GMT +8 hours)

Write a Python function that checks if a given list is sorted in descending order. Return None if the list is empty.

Sample Solution:

Code:

def is_descending_sorted(input_list):
    if not input_list:
        return None
    
    sorted_descending = all(input_list[i] >= input_list[i + 1] for i in range(len(input_list) - 1))
    return sorted_descending

def main():
    try:
       # nums = [7, 7, 8, 2, 1]
        nums  = [1, 2, 3, 4, 5]
        result = is_descending_sorted(nums)
        
        if result is None:
            print("List is empty.")
        elif result:
            print("List is sorted in descending order.")
        else:
            print("List is not sorted in descending order.")
    except Exception as e:
        print("An error occurred:", e)

if __name__ == "__main__":
    main()

Output:

List is not sorted in descending order.

List is not sorted in descending order.

In the above exercise, the "is_descending_sorted()" function checks if the input list is empty. If it's empty, it returns 'None'. Otherwise, it checks if all pairs of adjacent elements are descending by using a generator expression and the "all()" function. If all pairs are in descending order, it returns 'True'; otherwise, it returns 'False'. The "main()" function demonstrates the function's usage by providing a sample list of number.

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