The __str__ method__str__ is a special method, like __init__, that returns a 'informal' string representation of an object. It is useful in debugging.Consider the following code that uses the __str__ methodclass Time:     def __str__(self):         return '%.2d:%.2d:%.2d' % (self.hour, self.minute, self.second)When we print an object, Python invokes the str method −>>> time = Time(7, 36) >>> print time 07:36:00

The official Python documentation says __repr__() is used to compute the “official” string representation of an object. The repr() built-in function uses __repr__() to display the object. __repr__()  returns a printable representation of the object, one of the ways possible to create this object.  __repr__() is more useful for developers while __str__() is for end users.ExampleThe following code shows how __repr__() is used.class Point:    def __init__(self, x, y):      self.x, self.y = x, y    def __repr__(self):      return 'Point(x=%s, y=%s)' % (self.x, self.y) p = Point(3, 4) print pOutputThis gives ... Read More

The __del__() method is a known as a destructor method. It is called when an object is garbage collected which happens after all references to the object have been deleted.In a simple case this could be right after you delete a variable like del x or, if x is a local variable, after the function ends. In particular, unless there are circular references, CPython  which is the standard Python implementation will garbage collect immediately.The only property of Python garbage collection is that it happens after all references have been deleted, so this might not necessarily happen right after and even ... Read More

__init__ "__init__" is a reserved method in python classes. It is known as a constructor in OOP concepts. This method called when an object is created from the class and it allows the class to initialize the attributes of a class.How can we use  "__init__ " ?Let's consider that we are creating a class named Car. Car can have attributes like "color", "model", "speed" etc. and methods like "start", "accelarate", "change_ gear" and so on.Exampleclass Car(object):        def __init__(self, model, color, speed):              self.color = color              self.speed = ... Read More

In this article we are going to discuss how to create subclass from a super class in Python. Before proceeding further let us understand what is a class and a super class. A class is a user-defined template or prototype from which objects are made. Classes offer a way to bundle together functionality and data. The ability to create new instances of an object type is made possible by the production of a new class. Each instance of a class may have attributes connected to it to preserve its state. Class instances may also contain methods for changing their state ... Read More

Object-oriented programming creates reusable patterns of code to prevent code redundancy in projects. One way that recyclable code is created is through inheritance, when one subclass leverages code from another base class.Inheritance is when a class uses code written within another class.Classes called child classes or subclasses inherit methods and variables from parent classes or base classes.Because the Child subclass is inheriting from the Parent base class, the Child class can reuse the code of Parent, allowing the programmer to use fewer lines of code and decrease redundancy.Derived classes are declared much like their parent class; however, a list of ... Read More

The code below shows the if the attribute 'foo' was defined or derived in the classes A and B.Exampleclass A:     foo = 1 class B(A):     pass print A.__dict__ #We see that the attribute foo is there in __dict__ of class A. So foo is defined in class A. print hasattr(A, 'foo') #We see that class A has the attribute but it is defined. print B.__dict__ #We see that the attribute foo is not there in __dict__ of class B. So foo is not defined in class B print hasattr(B, 'foo') #We see that class B has ... Read More

We have the classes A and B defined as follows −class A(object): pass class B(A): passExampleA can be proved to be a super class of B in two ways as followsclass A(object):pass class B(A):pass print issubclass(B, A) # Here we use the issubclass() method to check if B is subclass of A print B.__bases__ # Here we check the base classes or super classes of BOutputThis gives the outputTrue (,)

We have the classes A and B defined as follows −class A(object): pass class B(A): passB can be proved to be a sub class of A in two ways as followsclass A(object):pass class B(A):pass print issubclass(B, A) # Here we use the issubclass() method to check if B is subclass of A print B.__bases__ # Here we check the base classes or super classes of BThis gives the outputTrue (,)

We can derive a class from multiple parent classes as follows −class A:        # define your class A ..... class B:         # define your class B ..... class C(A, B):   # subclass of A and B .....We can use isinstance() function to check the relationships of two classes and instances.Theisinstance(obj, Class) boolean function returns true if obj is an instance of class Class or is an instance of a subclass of Class