Dictionary Functions and Operations - Python Programming

PYTHON NOTES JEGAN K K
DICTIONARY IN PYTHON:
Dictionary in python is used in many forms namely for creating adjacency list for nodes/vertices in a
graph implementation and for json data loading in python.

It is a combination of keys and values.

Syntax = py_dict = dict() # for creating empty dictionary

py-dict = {1: 'Apple', 2: 'Mango'}

In the above example 1 & 2 are the keys and 'Apple' & 'Mango' are the respective values.



KEYS() - To get the keys alone from a dict we use keys() function.
Syntax => py_dict.keys()

VALUES() - To get the key’s corresponding value from python dictionary we use values() function.
Syntax => py_dict.values()

In certain scenario, if we need to convert a list of lists to a dictionary, the list must contain key and
value pairs respectively. So if there are more than 2 values in the sublists, it becomes invalid to pack
values in a dictionary.

Syntax => a = [[1,'Apple'], [2,'Mango']] # list of lists

py_dict = dict(a) # converted dict from list of list



ADDING ITEMS TO DICT:
a = dict()
a['Item1'] = 'Box' # {'Item1' : 'Box'}

To add new value and their key to a dictionary, the key is to be present inside the '[]' brackets like
dict[key] = value.



DELETING FROM DICTIONARY:
Syntax => del a[key]

To delete a key and its pair value, the del keyword along with the dict_name followed by [key] is used
respectively.