Introduction to Dictionaries - Concepts

The data type dictionary falls under mapping. 

• It is a mapping between a set of keys and a set of values. 
• The key-value pair is called an item. 
• A key is separated from its value by a colon(:) and consecutive items are separated by commas. 
• Items in dictionaries are unordered, so we may not get back the data in the same order in which we had entered the data initially in the dictionary.

Creating a dictionary

•  To create a dictionary, the items entered are separated by commas and enclosed in curly braces. 
• Each item is a key value pair, separated through colon (:). 
• The keys in the dictionary must be unique and should be of any immutable data type, i.e., number, string or tuple. 
• The values can be repeated and can be of any data type. 

Example:

Accessing items in a dictionary

The items of a dictionary are accessed via the keys rather than via their relative positions or indices. Each key serves as the index and maps to a value.

Example:

Dictionaries are Mutable

Dictionaries are mutable which implies that the contents of the dictionary can be changed after it has been created. 

Adding a new item

Example:

Modifying an existing item

The existing dictionary can be modified by just overwriting the key-value pair. 

Example: