A dictionary is an unordered data structure that allows you to store key-value pairs.

Suppose we have to create a dictionary named `student` with these
pairs:

`key is 'first name', value is 'Ann'`

`key is 'last name', value is 'Elliott'`

`key is 'city', value is 'New York'`

Let's look at the code to create this dictionary.


student = {'first name': 'Ann', 'last name': 'Elliot', 'city': 'New York'}

In the dictionary, the key can be any immutable data type. For example, the dictionary that we created in the example below uses the strings as keys. Let's create a dictionary where keys are numbers. 

countries = {4: 'Belgium', 2: 'Finland', 7: 'China', 5: 'Cyprus'}

It is important to note that the value of a particular key can be anything: strings, numbers, lists, and more.

What is a list?\nA list is a collection that is ordered and changeable. Moreover, this collection allows duplicate elements.

What is a dictionary?\nA dictionary is an ordered and changeable collection with no duplicate members.\n\nA dictionary holds `key:value` pairs. \n\nKey-value is provided in the dictionary to make it more optimized. 

What is a tuple?\nA tuple is a collection that is ordered and unchangeable. This collection allows duplicate elements.\nA tuple is a collection that is very similar to a list. The sequence of values stored in a tuple can be of any type, and they are indexed by integers. Values of a tuple are syntactically separated by ‘commas’. Although it is not necessary, it is more common to define a tuple by closing the sequence of values in parentheses. This helps to understand the Python tuples more easily.

What is a set?\nIn Python, a `set` is an `unordered collection` of data type that is `iterable`, `mutable` and has `no duplicate elements`. The order of elements in a set is undefined, though it may consist of various elements.\n\nThe major advantage of using a set as opposed to a list is that it has a highly optimized method for checking whether a specific element is contained in the set.