For example, for any bank employee who want to fetch the customer details online would go to customer class, where all its attributes like transaction details, withdrawal and deposit details, outstanding debt, etc. would be listed out.
How to define Python classes
How Inheritance works
Python Constructors
How to define Python classes
To define class you need to consider following points Step 1) In Python, classes are defined by the “Class” keyword Step 2) Inside classes, you can define functions or methods that are part of this class
Here we have defined method1 that prints “Guru99.” Another method we have defined is method2 that prints “Software Testing”+ SomeString. SomeString is the variable supplied by the calling method
Step 3) Everything in a class is indented, just like the code in the function, loop, if statement, etc. Anything not indented is not in the class
NOTE: About using “self” in Python
The self-argument refers to the object itself. Hence the use of the word self. So inside this method, self will refer to the specific instance of this object that’s being operated on. Self is the name preferred by convention by Pythons to indicate the first parameter of instance methods in Python. It is part of the Python syntax to access members of objects
Step 4) To make an object of the class Step 5) To call a method in a class
Notice that when we call the method1 or method2, we don’t have to supply the self-keyword. That’s automatically handled for us by the Python runtime. Python runtime will pass “self” value when you call an instance method on in instance, whether you provide it deliberately or not You just have to care about the non-self arguments
Step 6) Here is the complete code
How Inheritance works
Inheritance is a feature used in object-oriented programming; it refers to defining a new class with less or no modification to an existing class. The new class is called derived class and from one which it inherits is called the base. Python supports inheritance; it also supports multiple inheritances. A class can inherit attributes and behavior methods from another class called subclass or heir class.
Python Inheritance Syntax Step 1) Run the following code Notice that the in childClass, method1 is not defined but it is derived from the parent myClass. The output is “Guru99.” Step 2) Uncomment Line # 8 & 10. Run the code Now, the method 1 is defined in the childClass and output “childClass Method1” is correctly shown. Step 3) Uncomment Line #9. Run the code You can call a method of the parent class using the syntax In our case, we call, myClass.method1(self) and Guru99 is printed as expected Step 4) Uncomment Line #19. Run the code. Method 2 of the child class is called and “childClass method2” is printed as expected.
Python Constructors
A constructor is a class function that instantiates an object to predefined values. It begins with a double underscore (_). It init() method In below example we are taking name of the user using constructor. Output will be: Welcome to Guru99, Alex Python 2 Example Above codes are Python 3 examples, If you want to run in Python 2 please consider following code. Learn our next tutorial about Polymorphism in Python
Summary:
“Class” is a logical grouping of functions and data. Python class provides all the standard features of Object Oriented Programming.
Class inheritance mechanism A derived class that override any method of its base class A method can call the method of a base class with the same name Python Classes are defined by keyword “class” itself Inside classes, you can define functions or methods that are part of the class Everything in a class is indented, just like the code in the function, loop, if statement, etc. The self argument in Python refers to the object itself. Self is the name preferred by convention by Pythons to indicate the first parameter of instance methods in Python
Python runtime will pass “self” value automatically when you call an instance method on in instance, whether you provide it deliberately or not
In Python, a class can inherit attributes and behavior methods from another class called subclass or heir class.
