Working with Dictionaries

In this section, you will learn about dictionaries in Python. Dictionaries are unordered collections of key-value pairs. We will cover topics such as creating dictionaries, accessing values in a dictionary, dictionary methods (keys, values, items), modifying dictionaries, dictionary comprehension, and nested dictionaries.

Creating Dictionaries

In Python, you can create dictionaries by enclosing key-value pairs in curly braces {}. Here are some examples:

person = {
    "name": "John",
    "age": 25,
    "city": "New York"
}

car = dict(make="Toyota", model="Camry", year=2020)

Accessing Values in a Dictionary

You can access values in a dictionary by providing the corresponding key. Here’s an example:

person = {
    "name": "John",
    "age": 25,
    "city": "New York"
}

print(person["name"])  # Output: John
print(person["age"])   # Output: 25

Dictionary Methods

Python provides several built-in methods that can be used with dictionaries. Here are a few commonly used dictionary methods:

person = {
    "name": "John",
    "age": 25,
    "city": "New York"
}

keys = person.keys()        # Get the keys
values = person.values()    # Get the values
items = person.items()      # Get the key-value pairs

print(keys)    # Output: dict_keys(['name', 'age', 'city'])
print(values)  # Output: dict_values(['John', 25, 'New York'])
print(items)   # Output: dict_items([('name', 'John'), ('age', 25), ('city', 'New York')])

Modifying Dictionaries

You can modify dictionaries by assigning new values to existing keys or adding new key-value pairs. Here’s an example:

person = {
    "name": "John",
    "age": 25,
    "city": "New York"
}

person["age"] = 26        # Update value
person["country"] = "USA"  # Add new key-value pair

print(person)  # Output: {'name': 'John', 'age': 26, 'city': 'New York', 'country': 'USA'}