Overview of dictionary

In Python, a dictionary is a sequence of key-value, or item, pairs separated by commas.

Consider the following example:

port = {22: "SSH", 23: "Telnet" , 53: "DNS", 80: "HTTP" }

The port variable refers to a dictionary that contains port numbers as keys and its protocol names as values. 

Consider the following example:

companies = {"IBM": "International Business Machines", "L&T" :"Larsen & Toubro"}

The syntax of a dictionary is as follows:

Dictionary_name = {key: value}

The key-value pair is called an item. The key and value are separated by a colon (:), and each item is separated by a comma (,). The items are enclosed by curly braces ({ }). An empty dictionary can be created just by using curly braces ({ }). Key features of the dictionary are:

• The key of the dictionary can not be changed
• A string, int, or float can be used as a key
• A tuple that does not contain any list can be used as a key
• Keys are unique
• Values can be anything, for example, list, string, int, and so...