How to define a Python dictionary within dictionary?

A Dictionary in Python is a mutable, unordered collection of data in a key-value format. A dictionary can also contain another dictionary as a value, and this is known as a Nested Dictionary or a dictionary within a dictionary.

In this article, we are going to explore all the different ways to use a dictionary within a dictionary in Python.

Syntax to define a Dictionary within another

Following is the syntax of creating a Dictionary within another Dictionary in Python -

outer_dict = {
    'key1': {
        'inner_key1': 'value1',
        'inner_key2': 'value2'
    },
    'key2': {
        'inner_key1': 'value3',
        'inner_key2': 'value4'
    }
}

Note: We can access nested dictionary elements using multiple keys as outer_dict['key1']['inner_key1'].

Example-1: Create a basic Dictionary

In this example, we are going to create a basic Dictionary and then see how to create a Dictionary within a Dictionary -

# Creating a Dictionary
mydict = {
    'name': 'Riyaansh',
    'age': 30,
    'department': 'HR'
}

# Displaying the Dictionary
print("Dictionary = ", mydict)

# Length of the Dictionary
print("Dictionary Length = ", len(mydict))

Following is the output of the above program -

Dictionary =  {'name': 'Riyaansh', 'age': 30, 'department': 'HR'}
Dictionary Length =  3

Creating a Dictionary within a Dictionary

Here in this example, we will create a dictionary where each key maps to another dictionary that holds employee details -

# Creating a Dictionary within a Dictionary
employee_data = {
    'emp1': {'name': 'Riyaansh', 'age': 30, 'department': 'HR'},
    'emp2': {'name': 'Anil', 'age': 25, 'department': 'Engineering'},
    'emp3': {'name': 'Karthikeya', 'age': 28, 'department': 'Marketing'}
}

# Displaying the Dictionary
print("Employee Data = ", employee_data)

# Length of the Outer Dictionary
print("Total Employees = ", len(employee_data))

Below is the output of the above program -

Employee Data =  {'emp1': {'name': 'Riyaansh', 'age': 30, 'department': 'HR'}, 'emp2': {'name': 'Anil', 'age': 25, 'department': 'Engineering'}, 'emp3': {'name': 'Karthikeya', 'age': 28, 'department': 'Marketing'}}
Total Employees =  3

Accessing a Dictionary within a Dictionary

We can access the inner dictionary by using the keys of the dictionary. Here is an example of accessing the Dictionary within a Dictionary -

# Creating a Dictionary within a Dictionary
employee_data = {
    'emp1': {'name': 'Riyaansh', 'age': 30, 'department': 'HR'},
    'emp2': {'name': 'Anil', 'age': 25, 'department': 'Engineering'},
    'emp3': {'name': 'Karthikeya', 'age': 28, 'department': 'Marketing'}
}

# Accessing inner dictionary
print("emp2 Name = ", employee_data['emp2']['name'])
print("emp3 Department = ", employee_data['emp3']['department'])

Below is the output of the above program -

emp2 Name =  Anil
emp3 Department =  Marketing

Adding a New Inner Dictionary

In this example, we will add a new dictionary entry to our existing dictionary using a new key and value pair by using the assignment operator -

# Creating a Dictionary within a Dictionary
employee_data = {
    'emp1': {'name': 'Riyaansh', 'age': 30, 'department': 'HR'},
    'emp2': {'name': 'Anil', 'age': 25, 'department': 'Engineering'},
    'emp3': {'name': 'Karthikeya', 'age': 28, 'department': 'Marketing'}
}

# Adding new employee
employee_data['emp4'] = {'name': 'Niharikaa', 'age': 32, 'department': 'Finance'}

# Display the new employee record
print("emp4 Record = ", employee_data['emp4'])

Below is the output of the above program -

emp4 Record =  {'name': 'Niharikaa', 'age': 32, 'department': 'Finance'}

Looping through a Dictionary within a Dictionary

In this example, we will iterate over the outer dictionary and then over each inner dictionary to display complete all details of the employee information -

# Creating a Dictionary within a Dictionary
employee_data = {
    'emp1': {'name': 'Riyaansh', 'age': 30, 'department': 'HR'},
    'emp2': {'name': 'Anil', 'age': 25, 'department': 'Engineering'},
    'emp3': {'name': 'Karthikeya', 'age': 28, 'department': 'Marketing'},
    'emp4': {'name': 'Niharikaa', 'age': 32, 'department': 'Finance'}
}

# Looping through nested dictionaries
for emp_id, emp_info in employee_data.items():
    print(f"Employee ID: {emp_id}")
    for key, value in emp_info.items():
        print(f"  {key}: {value}")

Below is the output of the above program -

Employee ID: emp1
  name: Riyaansh
  age: 30
  department: HR
Employee ID: emp2
  name: Anil
  age: 25
  department: Engineering
Employee ID: emp3
  name: Karthikeya
  age: 28
  department: Marketing
Employee ID: emp4
  name: Niharikaa
  age: 32
  department: Finance

Access Specific Inner Dictionary Keys

We can access the specific values from the inner dictionary using exact outer key of the dictionary -

employee_data = {
    'emp1': {'name': 'Riyaansh', 'age': 30, 'department': 'HR'},
    'emp2': {'name': 'Anil', 'age': 25, 'department': 'Engineering'},
    'emp3': {'name': 'Karthikeya', 'age': 28, 'department': 'Marketing'},
    'emp4': {'name': 'Niharikaa', 'age': 32, 'department': 'Finance'}
}

# Specific access
print("emp1 Age = ", employee_data['emp1']['age'])
print("emp4 Department = ", employee_data['emp4']['department'])

Following is the output of the above program -

emp1 Age =  30
emp4 Department =  Finance