Sample code for the class example

Author: lpozo

python-class/README.md

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+# Python Classes: The Power of Object-Oriented Programming
+
+This folder provides the code examples for the article [Python Classes: The Power of Object-Oriented Programming](https://realpython.com/python-classes/).

python-class/abc_shapes.py

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+from abc import ABC, abstractmethod
+from math import pi
+
+
+class Shape(ABC):
+    @abstractmethod
+    def area(self):
+        pass
+
+    @abstractmethod
+    def perimeter(self):
+        pass
+
+
+class Circle(Shape):
+    def __init__(self, radius):
+        self.radius = radius
+
+    def area(self):
+        return pi * self.radius**2
+
+    def perimeter(self):
+        return 2 * pi * self.radius
+
+
+class Square(Shape):
+    def __init__(self, side):
+        self.side = side
+
+    def area(self):
+        return self.side**2
+
+    def perimeter(self):
+        return 4 * self.side
+
+
+circle = Circle(100)
+print(circle.radius)
+print(circle.area())
+print(circle.perimeter())

python-class/aircrafts.py

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+class Aircraft:
+    def __init__(self, thrust, lift, max_speed):
+        self.thrust = thrust
+        self.lift = lift
+        self.max_speed = max_speed
+
+    def technical_specs(self):
+        print(f"Thrust: {self.thrust} kW")
+        print(f"Lift: {self.lift} kg")
+        print(f"Max speed: {self.max_speed} km/h")
+
+
+class Helicopter(Aircraft):
+    def __init__(self, thrust, lift, max_speed, num_rotors):
+        super().__init__(thrust, lift, max_speed)
+        self.num_rotors = num_rotors
+
+    def technical_specs(self):
+        super().technical_specs()
+        print(f"Number of rotors: {self.num_rotors}")

python-class/animals.py

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+class Animal:
+    def __init__(self, name, gender, habitat):
+        self.name = name
+        self.gender = gender
+        self.habitat = habitat
+
+
+class Mammal(Animal):
+    unique_feature = "Mammary glands"
+
+
+class Bird(Animal):
+    unique_feature = "Feathers"
+
+
+class Fish(Animal):
+    unique_feature = "Gills"
+
+
+class Dog(Mammal):
+    def walk(self):
+        print("The dog is walking")
+
+
+class Cat(Mammal):
+    def walk(self):
+        print("The cat is walking")
+
+
+class Eagle(Bird):
+    def fly(self):
+        print("The eagle is flying")
+
+
+class Penguin(Bird):
+    def swim(self):
+        print("The penguin is swimming")
+
+
+class Salmon(Fish):
+    def swim(self):
+        print("The salmon is swimming")
+
+
+class Shark(Fish):
+    def swim(self):
+        print("The shark is swimming")

python-class/car.py

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+class Car:
+    def __init__(self, make, model, year, color):
+        self.make = make
+        self.model = model
+        self.year = year
+        self.color = color
+        self.started = False
+        self.speed = 0
+        self.max_speed = 200
+
+    def start(self):
+        print("Starting the car...")
+        self.started = True
+
+    def stop(self):
+        print("Stopping the car...")
+        self.started = False
+
+    def accelerate(self, value):
+        if not self.started:
+            print("Car is not started!")
+            return
+        if (speed := self.speed + value) <= self.max_speed:
+            print(f"Accelerating to {speed} km/h...")
+            self.speed += value
+        else:
+            print(f"Accelerating to {self.max_speed} km/h...")
+            self.speed = self.max_speed
+
+    def brake(self, value):
+        if (speed := self.speed - value) >= 0:
+            print(f"Braking to {speed} km/h...")
+            self.speed -= value
+        else:
+            print("Braking to 0 km/h...")
+            self.speed = 0
+
+    def __str__(self):
+        return f"{self.make}, {self.model}, {self.color}: ({self.year})"
+
+    def __repr__(self):
+        return (
+            f"{type(self).__name__}"
+            f'(make="{self.make}", '
+            f'model="{self.model}", '
+            f"year={self.year}, "
+            f'color="{self.color}")'
+        )

python-class/circle.py

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+import math
+
+
+class Circle:
+    def __init__(self, radius):
+        self.radius = radius
+
+    @property
+    def radius(self):
+        return self._radius
+
+    @radius.setter
+    def radius(self, value):
+        if (not isinstance(value, int | float)) or value <= 0:
+            raise ValueError("positive number expected")
+        self._radius = value
+
+    def area(self):
+        return round(math.pi * self._radius**2, 2)

python-class/counter.py

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+class ObjectCounter:
+    num_instances = 0
+
+    def __init__(self):
+        type(self).num_instances += 1

python-class/crafts.py

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+class Vehicle:
+    def __init__(self, make, model, color):
+        self.make = make
+        self.model = model
+        self.color = color
+
+    def start(self):
+        print("Starting the engine...")
+
+    def stop(self):
+        print("Stopping the engine...")
+
+    def technical_specs(self):
+        print(f"Make: {self.make}")
+        print(f"Model: {self.model}")
+        print(f"Color: {self.color}")
+
+
+class Car(Vehicle):
+    def drive(self):
+        print("Driving on the road...")
+
+
+class Aircraft(Vehicle):
+    def fly(self):
+        print("Flying on the sky...")
+
+
+class FlyingCar(Car, Aircraft):
+    pass

python-class/employee.py

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+from datetime import datetime
+
+
+class Employee:
+    company = "Example Inc."
+
+    def __init__(self, name, birth_date):
+        self.name = name
+        self.birth_date = birth_date
+
+    @property
+    def birth_date(self):
+        return self._birth_date
+
+    @birth_date.setter
+    def birth_date(self, value):
+        self._birth_date = datetime.fromisoformat(value)
+
+    def age(self):
+        today = datetime.today()
+        age = today.year - self.birth_date.year
+        birthday = datetime(
+            today.year, self.birth_date.month, self.birth_date.day
+        )
+        if today < birthday:
+            age -= 1
+        return age
+
+    @classmethod
+    def from_dict(cls, data_dict):
+        return cls(**data_dict)
+
+    def __str__(self):
+        return f"{self.name} is {self.age()} years old"
+
+    def __repr__(self):
+        return (
+            f"{type(self).__name__}("
+            f"name='{self.name}', "
+            f"birth_date='{self.birth_date.strftime('%Y-%m-%d')}')"
+        )

python-class/file_manager_srp.py

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+from pathlib import Path
+from zipfile import ZipFile
+
+# Bad example
+# class FileManager:
+#     def __init__(self, filename):
+#         self.filename = Path(filename)
+
+#     def read(self):
+#         with self.filename.open(mode="r") as file:
+#             data = file.read()
+#         return data
+
+#     def write(self, data):
+#         with self.filename.open(mode="w") as file:
+#             file.write(data)
+
+#     def compress(self):
+#         with ZipFile(self.filename.stem + ".zip", mode="w") as archive:
+#             archive.write(self.filename)
+
+#     def decompress(self, archive_name):
+#         with ZipFile(archive_name, mode="r") as archive:
+#             archive.extractall()
+
+
+# Good example
+class FileManager:
+    def __init__(self, filename):
+        self.filename = Path(filename)
+
+    def read(self):
+        with self.filename.open(mode="r") as file:
+            data = file.read()
+        return data
+
+    def write(self, data):
+        with self.filename.open(mode="w") as file:
+            file.write(data)
+
+
+class ZipFileArchiver:
+    def __init__(self, filename):
+        self.filename = Path(filename)
+
+    def compress(self):
+        with ZipFile(self.filename.stem + ".zip", mode="w") as archive:
+            archive.write(self.filename)
+
+    def decompress(self, archive_name):
+        with ZipFile(archive_name, mode="r") as archive:
+            archive.extractall()