Python Nested Dictionaries Course
Introduction to Nested Dictionaries
In Python, dictionaries are data structures that store key-value pairs. A nested dictionary is simply a dictionary that contains other dictionaries as its values. This allows you to create complex, hierarchical data structures.
Creating Nested Dictionaries
A nested dictionary is created using the standard dictionary syntax, but with dictionaries as values. Here’s a simple example:
# Creating a nested dictionary
person = {
"name": "Alice",
"address": {
"street": "123 Main St",
"city": "Paris",
"postal_code": "75001"
},
"contacts": {
"email": "alice@example.com",
"phone": "0123456789"
}
}
Accessing Items in a Nested Dictionary
To access an item in a nested dictionary, you use the keys for each level of the structure. Here’s how to access specific items from the person dictionary:
# Accessing the name
name = person["name"]
print(name) # Output: Alice
# Accessing the address
address = person["address"]
print(address) # Output: {'street': '123 Main St', 'city': 'Paris', 'postal_code': '75001'}
# Accessing the street
street = person["address"]["street"]
print(street) # Output: 123 Main St
# Accessing the phone number
phone = person["contacts"]["phone"]
print(phone) # Output: 0123456789
Looping Through Nested Dictionaries
You can use loops to iterate through the items in a nested dictionary. Here are some examples:
Loop Through Keys and Values
To loop through the keys and values of a nested dictionary, you can use for loops. Here’s an example:
# Looping through the keys and values of the address
for key, value in person["address"].items():
print(f"{key}: {value}")
# Output:
# street: 123 Main St
# city: Paris
# postal_code: 75001
Loop Through Nested Dictionaries
To loop through the nested dictionaries themselves, you can use nested loops:
# Looping through nested dictionaries
for category, info in person.items():
print(f"Category: {category}")
if isinstance(info, dict):
for key, value in info.items():
print(f" {key}: {value}")
else:
print(f" {info}")
# Output:
# Category: name
# Alice
# Category: address
# street: 123 Main St
# city: Paris
# postal_code: 75001
# Category: contacts
# email: alice@example.com
# phone: 0123456789
Modifying Values in a Nested Dictionary
You can modify values in a nested dictionary similarly to how you modify values in a flat dictionary. Here’s how to update information in the person dictionary:
# Modifying the street
person["address"]["street"] = "456 New St"
# Adding a new contact
person["contacts"]["mobile"] = "0987654321"
print(person)
# Output:
# {
# 'name': 'Alice',
# 'address': {
# 'street': '456 New St',
# 'city': 'Paris',
# 'postal_code': '75001'
# },
# 'contacts': {
# 'email': 'alice@example.com',
# 'phone': '0123456789',
# 'mobile': '0987654321'
# }
# }
Deleting Items from a Nested Dictionary
To delete items, use the del statement to remove specific keys:
# Deleting the phone number
del person["contacts"]["phone"]
print(person)
# Output:
# {
# 'name': 'Alice',
# 'address': {
# 'street': '456 New St',
# 'city': 'Paris',
# 'postal_code': '75001'
# },
# 'contacts': {
# 'email': 'alice@example.com',
# 'mobile': '0987654321'
# }
# }
Conclusion
Nested dictionaries are powerful for organizing hierarchical data. By understanding how to create, access, modify, and loop through these structures, you can efficiently manage complex data in Python.