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Defining and Using Classes

Yasin Cakal

In Python, a class is a template for creating objects. Objects have member variables and have behavior associated with them. In Python, a class is created by the keyword “class” followed by the name of the class.

For example, consider the following code:

class Dog:
    def __init__(self, name, age):
        self.name = name
        self.age = age

The “Dog” class has a member variable “name” and a member variable “age”. The “init” method is a special method in Python that is used to initialize the object when it is created. The “self” keyword refers to the object itself.

Creating an Object

To create an object from a class, you use the class name followed by parentheses. For example, to create an object from the “Dog” class, you can use the following code:

dog1 = Dog("Fido", 3)

To access the member variables of an object, you use the dot operator. For example, to access the “name” member variable of the “dog1” object, you can use the following code:

print(dog1.name)

To define a method in a class, you use the keyword “def” followed by the method name and the method parameters. For example, consider the following code:

class Dog:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def bark(self):
        print("Woof!")

To call a method of an object, you use the dot operator followed by the method name and the method parameters. For example, to call the “bark” method of the “dog1” object, you can use the following code:

dog1.bark()

Conclusion

Using classes and objects in Python allows you to create reusable code and model real-world entities in your programs. It is an important concept to understand in Python, and one that you will encounter frequently as you continue to learn and develop your Python skills.

Exercises

Here are some exercises with solutions to help you practice what you just learned:

How do you create an object from a class in Python?

To create an object from a class in Python, you use the class name followed by parentheses. For example, to create an object from the “Dog” class, you can use the following code:

dog1 = Dog()

How do you access the member variables of an object in Python?

To access the member variables of an object in Python, you use the dot operator followed by the name of the member variable. For example, consider the following code:

class Dog:
    def __init__(self, name, age):
        self.name = name
        self.age = age

dog1 = Dog("Fido", 3)
print(dog1.name)

n the above example, the “name” member variable of the “dog1” object is accessed using the dot operator.

How do you call a method of an object in Python?

To call a method of an object in Python, you use the dot operator followed by the method name and the method parameters. The method parameters are defined within parentheses and are separated by commas. For example, consider the following code:

class Dog:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def bark(self):
        print("Woof!")

dog1 = Dog("Fido", 3)
dog1.bark()

In the above example, the “bark” method of the “dog1” object is called using the dot operator.

How do you pass arguments to a method of an object in Python?

To pass arguments to a method of an object in Python, you include the arguments in the method call within parentheses and separate them with commas. For example, consider the following code:

class Dog:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def bark(self, num_times):
        for i in range(num_times):
            print("Woof!")

dog1 = Dog("Fido", 3)
dog1.bark(3)

In the above example, the “bark” method of the “dog1” object is called with the argument “3”, which specifies that the method should print “Woof!” three times.

How do you pass multiple arguments to a method of an object in Python?

To pass multiple arguments to a method of an object in Python, you include the arguments in the method call within parentheses and separate them with commas. For example, consider the following code:

class Dog:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def bark(self, num_times, sound):
        for i in range(num_times):
            print(sound)

dog1 = Dog("Fido", 3)
dog1.bark(3, "Woof!")

In the above example, the “bark” method of the “dog1” object is called with the arguments “3” and “Woof!”, which specify that the method should print “Woof!” three times.

Introduction to Python

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