Python Nested Dictionary

Prerequisite – Python dictionary
A Dictionary in Python works similar to the Dictionary in the real world. Keys of a Dictionary must be unique and of immutable data type such as Strings, Integers and tuples, but the key-values can be repeated and be of any type.
Nested Dictionary: Nesting Dictionary means putting a dictionary inside another dictionary. Nesting is of great use as the kind of information we can model in programs is expanded greatly. 

Python3

nested_dict = { 'dict1': {'key_A': 'value_A'},
                'dict2': {'key_B': 'value_B'}}

Python3

# As shown in image

# Creating a Nested Dictionary
Dict = {1: 'Geeks', 2: 'For', 3: {'A' : 'Welcome', 'B' : 'To', 'C' : 'Geeks'}}

Creating a Nested Dictionary

In Python, a Nested dictionary can be created by placing the comma-separated dictionaries enclosed within braces. 

Python3

# Empty nested dictionary
Dict = { 'Dict1': { },
         'Dict2': { }}
print("Nested dictionary 1-")
print(Dict)

# Nested dictionary having same keys
Dict = { 'Dict1': {'name': 'Ali', 'age': '19'},
         'Dict2': {'name': 'Bob', 'age': '25'}}
print("\nNested dictionary 2-")
print(Dict)

# Nested dictionary of mixed dictionary keys
Dict = { 'Dict1': {1: 'G', 2: 'F', 3: 'G'},
         'Dict2': {'Name': 'Geeks', 1: [1, 2]} }
print("\nNested dictionary 3-")
print(Dict)

Output:

Nested dictionary 1-
{'Dict1': {}, 'Dict2': {}}

Nested dictionary 2-
{'Dict1': {'name': 'Ali', 'age': '19'}, 'Dict2': {'name': 'Bob', 'age': '25'}}

Nested dictionary 3-
{'Dict1': {1: 'G', 2: 'F', 3: 'G'}, 'Dict2': {1: [1, 2], 'Name': 'Geeks'}}

Adding elements to a Nested Dictionary

Addition of elements to a nested Dictionary can be done in multiple ways. One way to add a dictionary in the Nested dictionary is to add values one be one, Nested_dict[dict][key] = ‘value’. Another way is to add the whole dictionary in one go, Nested_dict[dict] = { ‘key’: ‘value’}. 

Python3

Dict = { }
print("Initial nested dictionary:-")
print(Dict)

Dict['Dict1'] = {}

# Adding elements one at a time
Dict['Dict1']['name'] = 'Bob'
Dict['Dict1']['age'] = 21
print("\nAfter adding dictionary Dict1")
print(Dict)

# Adding whole dictionary
Dict['Dict2'] = {'name': 'Cara', 'age': 25}
print("\nAfter adding dictionary Dict1")
print(Dict)

Output:

Initial nested dictionary:-
{}

After adding dictionary Dict1
{'Dict1': {'age': 21, 'name': 'Bob'}}

After adding dictionary Dict1
{'Dict1': {'age': 21, 'name': 'Bob'}, 'Dict2': {'age': 25, 'name': 'Cara'}}

Access elements of a Nested Dictionary

In order to access the value of any key in nested dictionary, use indexing [] syntax. 

Python3

# Nested dictionary having same keys
Dict = { 'Dict1': {'name': 'Ali', 'age': '19'},
         'Dict2': {'name': 'Bob', 'age': '25'}}

# Prints value corresponding to key 'name' in Dict1
print(Dict['Dict1']['name'])

# Prints value corresponding to key 'age' in Dict2
print(Dict['Dict2']['age'])

Output:

Ali
25

Deleting dictionaries from a Nested Dictionary

Deletion of dictionaries from a nested dictionary can be done either by using del keyword or by using pop() function. 

Python3

Dict = {'Dict1': {'name': 'Ali', 'age': 19},
        'Dict2': {'name': 'Bob', 'age': 21}}
print("Initial nested dictionary:-")
print(Dict)

# Deleting dictionary using del keyword
print("\nDeleting Dict2:-")
del Dict['Dict2']
print(Dict)

# Deleting dictionary using pop function
print("\nDeleting Dict1:-")
Dict.pop('Dict1')
print (Dict)

Output:

Initial nested dictionary:-
{'Dict2': {'name': 'Bob', 'age': 21}, 'Dict1': {'name': 'Ali', 'age': 19}}

Deleting Dict2:-
{'Dict1': {'name': 'Ali', 'age': 19}}

Deleting Dict1:-
{}