Python Program - Flatten a Nested List

here's a Python program that flattens a nested list:

def flatten_list(nested_list):
    """
    Flattens a nested list.

    Args:
        nested_list: A nested list.

    Returns:
        A flattened list.
    """
    flattened_list = []
    for item in nested_list:
        if isinstance(item, list):
            # recursively call flatten_list if item is a list
            flattened_list.extend(flatten_list(item))
        else:
            flattened_list.append(item)
    return flattened_list

# Example usage:
nested_list = [[1, 2, [3]], 4]
flattened_list = flatten_list(nested_list)
print(flattened_list) # Output: [1, 2, 3, 4]

In this program, we define a function called flatten_list() that takes a nested list as its argument, and returns a flattened list.

Inside the function, we first create an empty list called flattened_list.

We then loop through each item in the input nested_list. If the item is a list, we recursively call flatten_list() on that item, and extend flattened_list with the flattened list returned by that call. If the item is not a list, we simply append it to flattened_list.

Finally, we return the flattened list.

In the example usage, we create a nested list [[1, 2, [3]], 4], and call flatten_list() on it to get the flattened list [1, 2, 3, 4]. We then print out the flattened list using the print() function.