如何通过特定格式的用户输入来更改列表中的值？

def update_list(user_input, original_list):
    try:
        index, new_value = user_input.split(':')
        index = int(index)
        if 0 <= index < len(original_list):
            original_list[index] = new_value
            return True, original_list
        else:
            return False, "Index out of range"
    except ValueError:
        return False, "Invalid input format"

# 示例使用
my_list = ['apple', 'banana', 'cherry']
user_input = "2:new_item"
success, result = update_list(user_input, my_list)

if success:
    print("List updated successfully:", result)
else:
    print("Error:", result)