Python Class

Python is an Object-Oriented Programming Language (OOPS). It means everything in python is an object or instance of some class. In simple words, the Python class is a blueprint of an object. Or it is a combination of initializing variables, defining methods, static methods, etc.

In this section, we explain to you how to create a class in Python object oriented programming, creating an object or instance attributes, Modify Object, delete an object, or class instances with examples.

Creating an Empty Class in Python

If you want to create a Python class that does nothing or creates an empty one, you must use the pass keyword.

class Employee:
    pass

The following example shows how to declare a variable and create a method inside a Python classes. There are different kinds of methods, which we discuss in the later section. For now, understand the class in python syntax.

class Employee:
    Variable = Value
 

    def function_name(self):
        Statements 
    …………..

Python class Object

In Python, class objects supports both the attribute reference and instantiation. You can use either of them to call the class attributes. It is an example of both the instantiation and the attribute reference.

• The attribute reference uses CLName.Variable_name or CLName.function_name.
• For the instantiation, you have to create an instance or a copy of that Python classes. To create a new instance use instance_name = CLName(), to call the variable instance_name.variable_name and to call the method instance_name.method_name()

Here, emp = Employee() is creating an instantiation, and emp.company inside print means calling class variable. Next, Employee.company is an example of a Python class attribute reference.

class Employee:
    company = 'Tutorial Gateway'
 
emp = Employee()
print(emp.company)
 
print("-------------")
print(Employee.company)

Tutorial Gateway
-------------
Tutorial Gateway

In this Python classes example, we declared a variable company, and we defined a function with a self parameter that prints a welcome message. Next, we created an object emp1 for Employee. By using this object emp1, we are accessing the company variable, and func_message().

Within the last two statements, we used the attribute reference to access the variable value and the function result. By using attribute reference, you can print the variable value. However, Employee.func_message returns the function object but not the actual function result. So, you should remember this concept while working with attribute references in a python classes.

class Employee:
    company = 'Tutorial Gateway'
 
    def func_message(self):
        print('Welcome to Programming')
 
emp = Employee()
print(emp.company)
emp.func_message()
 
print("-------------")
print(Employee.company)
print(Employee.func_message)

Tutorial Gateway
Welcome to Programming
-------------
Tutorial Gateway
<function Employee.func_message at 0x7f831ddd8d30>

Python __init() function

By default, all the Python classes in real-time have an __init__() function. Use this function to assign values to the properties of an object. When you create an object of a class in Python, it automatically calls the __init__() function. You don’t have to call it.

In this Python example, we used a simple print statement inside an __init__() function. Next, we created an object of Employee. As you can see, it is directly printing the message.

class Employee:
    company = 'Tutorial Gateway'

    def __init__(self):
        print('Hello World')
 
    def func_message(self):
        print('Welcome to Python Programming')
 
emp1 = Employee() # Created an Instance
 
print(emp1.company)
emp1.func_message()

Here, we use the __init__() function to add values to the class properties in Python. Here, we used name, age, gender in the function, and assigned those values in the next line. It means, when you create an object of employee, you have to provide the name, age, and gender (while creating the object itself).

For instance, if you create an object emp1 = Employee() without the argument values, then the following error raised. TypeError: __init__() missing 3 required positional arguments: ‘name’, ‘age’, and ‘gender’

class Employee:
    company = 'Tutorial Gateway'
 
    def __init__(self, name, age, gender):
        self.name = name
        self.age = age
        self.gender = gender
 
    def func_message(self):
        print('Welcome to Programming')
 
emp1 = Employee('Jack', 25, 'Male') 

print(emp1.company)
emp1.func_message()
print(emp1.name)
print(emp1.age)
print(emp1.gender)

init output

Tutorial Gateway
Welcome to Programming
Jack
25
Male

From the above Python classes example, it might confuse you to declare the argument because we used the same names: name, age, gender all the time. However, it is not mandatory to use like that, but it is a best practice to do so.

In this Python example, we are using n, a, gen as __init__ arguments and name, age, gender as self initialization of a class. Hopefully, this might clear your confusion.

class Employee:
    company = 'Tutorial Gateway'

    def __init__(self, n, a, gen):
        self.name = n
        self.age = a
        self.gender = gen

    def func_message(self):
        print('Welcome to Programming')

emp1 = Employee('Johnson', 29, 'Male')
 
print(emp1.company)
emp1.func_message()
print(emp1.name)
print(emp1.age)
print(emp1.gender)

init output

Tutorial Gateway
Welcome to Programming
Johnson
29
Male

Multiple class Objects in Python

When you create a Python object or instance of a class, it holds a copy of that, not the actual one. It means you can create n number of objects from a single one, and each instance might have different property values or method values.

In this Python example, we created an Employee class. Next, we created two objects emp1 and emp2 from that employee. As you can see, each instance has different names, ages, and gender. Next, we are printing those values as output, and you can see they work!.

class Employee:
    company = 'Tutorial Gateway'

    def __init__(self, name, age, gender):
        self.name = name
        self.age = age
        self.gender = gender
 
    def func_message(self):
        print('Welcome to this World')
 
emp1 = Employee('Mike', 25, 'Male')
print(emp1.company)
emp1.func_message()
print(emp1.name)
print(emp1.age)
print(emp1.gender)
 
print()
emp2 = Employee('Tracy', 27, 'Female')
print(emp2.company)
emp2.func_message()
print(emp2.name)
print(emp2.age)
print(emp2.gender)

Tutorial Gateway
Welcome to this World
Mike
25
Male

Tutorial Gateway
Welcome to this World
Tracy
27
Female

This Python classes example is the same as above. However, this time we modified the func_message(self) function definition. It accepts the name (instance variable) and attaches to the message that we print as an output. Let me call this message from two instances emp1 and emp2.

class Employee:
    company = 'Tutorial Gateway'

    def __init__(self, name, age, gender):
        self.name = name
        self.age = age
        self.gender = gender
 
    def func_message(self):
        print(self.name + ' is learning Programming')
 
emp1 = Employee('Mike', 25, 'Male')
print(emp1.company)
print(emp1.name) # Mike
print(emp1.age) #25
print(emp1.gender)
emp1.func_message()
 
print()
emp2 = Employee('Tracy', 27, 'Female')
print(emp2.company)
print(emp2.name) #Tracy
print(emp2.age) # 27
print(emp2.gender)
emp2.func_message()

As you can see emp1.func_message() replaced the self.name as Mike and emp2.func_message() replaced self.name with Tracy.

Tutorial Gateway
Mike
25
Male
Mike is learning Programming

Tutorial Gateway
Tracy
27
Female
Tracy is learning Programming

Modifying the Python Class Variable example

Let us see how to modify the Python classes variable using the Objects. First, we declared a company variable and a function that prints a welcome message. Next, we created three instances emp1, emp2, and emp3 of the Employee.

Next, we used Object_name.Variabel_name = New_Name to change the name of the company for emp2 and emp3 objects. It changes the company names for both of these instances. Next, we are printing the company variable from all these three instances.

class Employee:
    company = 'Tutorial Gateway'
 
    def func_message(self):
        print('Welcome to Programming')
 
emp1 = Employee()
emp2 = Employee()
emp3 = Employee()
 
emp2.company = 'Py'
emp3.company = 'Apple'
 
emp1.func_message()
 
print(emp1.company)
print(emp2.company)
print(emp3.company)
print(emp1.company)

Welcome to Programming
Tutorial Gateway
Py
Apple
Tutorial Gateway

Modify Python Class Object Properties

This example shows how to modify the Object Properties. First, we created an instance emp1 of the Employee with the required fields. Next, we are printing the available values as an output.

Here, emp1.name = ‘John’ (object_name.property_name = New_Value) statement updates the existing emp1 name (Mike) to John. Let me check the same by printing the emp1 name one more time.

class Employee:
    company = 'Tutorial Gateway'

    def __init__(self, name, age, gender):
        self.name = name
        self.age = age
        self.gender = gender
 
    def func_message(self):
        print(self.name + ' is learning Programs')

emp1 = Employee('Mike', 25, 'Male')
print(emp1.name)
print(emp1.age)
print(emp1.gender)
emp1.func_message()
 
emp1.name = 'John'
print(emp1.name)
emp1.func_message()

See that the last two statements are printing the new name, John.

Mike
25
Male
Mike is learning Programs
John
John is learning Programs

Delete Python Object Properties

In this example, we show how to delete an object property. Here, emp1 = Employee(‘John’, 25, ‘Male’) creates an instance emp1 for Employee. Next, we are printing the name, age, gender, and the message from the func_message() method.

Next, we used the del keyword to delete the emp1 object property called name (del instance_name.property_name). Within the last statement, we again printed the name property of the emp1 object that we deleted. As you can see, it displays an error ‘Employee’ object has no attribute’ name’. It means we successfully deleted the object property. Similarly, you can delete age by del emp1.age and gender by del emp1.gender.

class Employee:
    company = 'Tutorial Gateway'
 
    def __init__(self, name, age, gender):
        self.name = name
        self.age = age
        self.gender = gender
 
    def func_message(self):
        print(self.name + ' is learning Programming')
 
emp1 = Employee('John', 25, 'Male')
print(emp1.name)
print(emp1.age)
print(emp1.gender)
emp1.func_message()
 
del emp1.name 
print(emp1.name)

John
25
Male
John is learning Programming
Traceback (most recent call last):
  File "/Users/suresh/Desktop/simple.py", line 19, in <module>
    print(emp1.name)
AttributeError: 'Employee' object has no attribute 'name'

Remember, deleting an instance property doesn’t affect the other instance property. This Python classes example is the same as above. However, this time we created two Instances emp1 and emp2 for the Employee. Next, we deleted the name property of the emp1 object using the del keyword. Next, we are printing the name of emp2 instance and emp1 instance.

emp2.name returns the name as Nancy but emp1.name is throwing an error because we deleted it previously.

class Employee:
    company = 'Tutorial Gateway'
 
    def __init__(self, name, age, gender):
        self.name = name
        self.age = age
        self.gender = gender
 
    def func_message(self):
        print(self.name + ' is learning Programming')
 
emp1 = Employee('John', 25, 'Male')
emp2 = Employee('Nancy', 27, 'Female')
print(emp1.name)
print(emp1.age)
print(emp1.gender)
emp1.func_message()
 
del emp1.name
print(emp2.name)
print(emp1.name)

John
25
Male
John is learning Programming
Nancy
Traceback (most recent call last):
  File "/Users/suresh/Desktop/simple.py", line 21, in <module>
    print(emp1.name)
AttributeError: 'Employee' object has no attribute 'name'

Delete Python Classes and Objects

In this Python classes example, we use the same that we defined in our previous example. Here, first, we create an object of Employee and displaying the employee name, age, gender, and the message from the func_message() method. Please refer static methods article.

Next, we used the del keyword to delete the object emp1 (del Object_name). It deletes the instance emp1 that we created earlier. In the last statement, we called the func_message() method with an emp1 object to check whether the object still exists or not. As you see, it was throwing an error name ’emp1′ is not defined. It means, we deleted the emp1 object by the del statement.

class Employee:
    company = 'Tutorial Gateway'
 
    def __init__(self, name, age, gender):
        self.name = name
        self.age = age
        self.gender = gender
 
    def func_message(self):
        print(self.name + ' is learning Programming')
 
emp1 = Employee('John', 25, 'Male')
print(emp1.name)
print(emp1.age)
print(emp1.gender)
emp1.func_message()
 
del emp1
emp1.func_message()

John
25
Male
John is learning Programming
Traceback (most recent call last):
  File "/Users/suresh/Desktop/simple.py", line 19, in <module>
    emp1.func_message()
NameError: name 'emp1' is not defined

Creating Python class example

Here, we show the different ways to create a class in python. As you can see, either you can use c_name Employee, c_name(), or c_name(object). The last option with the object is the latest one to create a class in python. If you look close to object creation, we used the same approach to create the object for all those three.

class Employee:
    def __init__(self):
        print('Msg from Employee : Welcome to Tutorial Gateway')
 
class Student():
    def __init__(self):
        print('Msg from Student: Hello World!')
 
class Person(object):
    def __init__(self):
        print('Msg from Person: Welcome to Programming')
         
emp = Employee()

std = Student()

per = Person()

create using a c_name or c_name() output

Msg from Employee : Welcome to Tutorial Gateway
Msg from Student: Hello World!
Msg from Person: Welcome to Programming

Python class self parameter

The Python self parameter is nothing but a reference to the current instance of a class. We have to use this Python class self parameter as the first parameter, which helps us to access the variables.

If you don’t like the keyword self, then use any word as a self parameter. However, it has to be the first parameter. In this Python classes example, we used suresh instead of self in the third method.

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

    def func_message(self):
        print(self.name + ' is learning Programming')
 
    def func_msg(suresh):
        print('Tutorial Gateway Welcome ' + suresh.name)
 
emp1 = Employee('John', 25)
emp1.func_message()
emp1.func_msg()

John is learning Programming
Tutorial Gateway Welcome John