Master Python Loops, Dictionaries, and OOP Basics with Practical Examples

Welcome back to our Python learning series. In the previous article we covered lists and dictionaries; now we continue with iteration and object‑oriented programming.

For Loops and Iterators

Python makes iterating over a list straightforward with a for loop:

bookshelf = [
    "传习录",
    "禅与摩托车修理技术",
    "Python 从Zero到Hero",
    "从零到一",
    ""
]
for book in bookshelf:
    print(book)

The code prints each book title in order.

Iterating over a dictionary requires accessing its keys:

dictionary = { "some_key": "some_value" }
for key in dictionary:
    print("%s --> %s" % (key, dictionary[key]))

Output: #some_key --> some_value You can also iterate over key‑value pairs directly:

dictionary = { "some_key": "some_value" }
for key, value in dictionary.items():
    print("%s --> %s" % (key, value))

The result is the same. The variable names are arbitrary, as shown here:

dictionary_ex = {
    "name": "Raymond",
    "nickname": "Luoyi",
    "nationality": "China",
    "age": 38
}
for attribute, value in dictionary_ex.items():
    print("My %s is %s" % (attribute, value))

Output:

# My name is Raymond
# My nickname is Luoyi
# My nationality is China
# My age is 38

Classes and Objects

Objects model real‑world entities such as cars, cats, or washing machines, encapsulating data (attributes) and behavior (methods). In Python, a class serves as a blueprint:

class Vehicle:
    pass

Create an instance:

car = Vehicle()
print(car)  # <__main__.Vehicle object at 0x...>

Define a constructor to initialise attributes:

class Vehicle:
    def __init__(self, number_of_wheels, type_of_tank, seating_capacity, maximum_velocity):
        self.number_of_wheels = number_of_wheels
        self.type_of_tank = type_of_tank
        self.seating_capacity = seating_capacity
        self.maximum_velocity = maximum_velocity

Instantiate a specific vehicle: tesla_model_s = Vehicle(4, 'electric', 5, 250) Implement getters and setters (traditional methods):

class Vehicle:
    def __init__(self, number_of_wheels, type_of_tank, seating_capacity, maximum_velocity):
        self.number_of_wheels = number_of_wheels
        # other attributes omitted for brevity
    def number_of_wheels(self):
        return self.number_of_wheels
    def set_number_of_wheels(self, number):
        self.number_of_wheels = number

Python’s @property decorator provides a cleaner approach:

class Vehicle:
    def __init__(self, number_of_wheels, type_of_tank, seating_capacity, maximum_velocity):
        self._number_of_wheels = number_of_wheels
        # other attributes omitted
    @property
    def number_of_wheels(self):
        return self._number_of_wheels
    @number_of_wheels.setter
    def number_of_wheels(self, number):
        self._number_of_wheels = number

Using the property:

tesla_model_s = Vehicle(4, 'electric', 5, 250)
print(tesla_model_s.number_of_wheels)  # 4
tesla_model_s.number_of_wheels = 2
print(tesla_model_s.number_of_wheels)  # 2

Another example method demonstrates custom behavior:

class Vehicle:
    def __init__(self, number_of_wheels, type_of_tank, seating_capacity, maximum_velocity):
        self.number_of_wheels = number_of_wheels
        # other attributes omitted
    def make_noise(self):
        print('VRUUUUUUUM')

Calling the method:

tesla_model_s = Vehicle(4, 'electric', 5, 250)
tesla_model_s.make_noise()  # VRUUUUUUUM

Future topics will cover encapsulation (hiding data and methods) and inheritance.

Author: 21CTO Community – This article is part of a Python development series.