Objects and Lists

Dictionaries

A dictionary is a collection of key-value pairs. It is used to store structured data.

Creating a Dictionary

Dictionaries are created using curly braces {} with keys and values separated by colons.

pythonCopyEditperson = {
    "name": "Alice",
    "age": 30
}

Accessing Dictionary Values

Values can be accessed using square brackets or the get() method.

pythonCopyEditprint(person["name"])      # Dot notation is not used in Python
print(person.get("age"))   # Safe access, returns None if key doesn’t exist

Modifying Dictionary Values

You can update existing properties or add new ones dynamically.

pythonCopyEditperson["age"] = 31         # Modify existing value
person["city"] = "London"  # Add new property

Deleting Dictionary Entries

Use the del keyword to remove a key-value pair.

pythonCopyEditdel person["age"]

Iterating Over Dictionaries

Use a for loop to iterate over keys and values.

pythonCopyEditfor key, value in person.items():
    print(f"{key}: {value}")

Lists in Python

A list is an ordered collection of values.

Creating a List

pythonCopyEditfruits = ["apple", "banana", "cherry"]

Adding and Removing Elements

• append(value) – Adds to the end

• pop() – Removes the last item

• insert(index, value) – Adds at specific position

• remove(value) – Removes first matching value

pythonCopyEditfruits.append("orange")
fruits.pop()
fruits.insert(0, "grape")
fruits.remove("banana")

Nested Dictionaries and Lists

Dictionaries can contain lists, and lists can contain dictionaries.

pythonCopyEdituser = {
    "name": "Alice",
    "hobbies": ["reading", "cycling"]
}

users = [
    {"name": "Bob", "age": 25},
    {"name": "Eve", "age": 28}
]

Conclusion

Dictionaries and lists are essential for managing and structuring data in Python. They are widely used for everything from simple data storage to complex data modeling. In the next section, we’ll explore modern Python features, including comprehensions, unpacking, and f-strings, which enhance productivity and readability.