Write a program that appends the contents of one file to another. Have the program take the filenames from the user.

Here’s a Python program that allows the user to enter the names of the source file and the destination file, and then appends the contents of the source file to the destination file:

def append_file(source_file, destination_file):
    try:
        with open(source_file, 'r') as source:
            with open(destination_file, 'a') as destination:
                destination.write(source.read())
        print(f"Contents of '{source_file}' appended to '{destination_file}'.")

    except FileNotFoundError:
        print("One or both files not found.")


source_file = input("Enter the name of the source file: ")
destination_file = input("Enter the name of the destination file: ")

append_file(source_file, destination_file)

When you run the program, it will prompt you to enter the name of the source file and the destination file. It then opens both files, reads the contents of the source file using read(), and appends the contents to the destination file using write() with the mode set to 'a' for append. Finally, it prints a success message if the operation is successful. If either of the files is not found, it prints an error message.