python add to list if not in list

in python, a dictionary is a versatile data structure that allows you to store and organize data in key-value pairs. each key in the dictionary must be unique, and it is associated with a value. dictionaries are incredibly useful for tasks like storing configurations, mapping relationships, and more. this tutorial will guide you through the process of adding elements to a dictionary in python.
a dictionary in python is defined using curly braces {}. each element in the dictionary consists of a key and its corresponding value, separated by a colon :. the keys are usually strings or numbers, while values can be of any data type, including strings, numbers, lists, other dictionaries, or even custom objects.
to add elements to a dictionary, you can use either of these two methods:
if you want to update the value of an existing key in the dictionary, you can simply reassign the value using as ...