Python Classes and ObjectsPython Classes/ObjectsPython is an object oriented programming language. Show
Almost everything in Python is an object, with its properties and methods. A Class is like an object constructor, or a "blueprint" for creating objects. Create a ClassTo create a class, use the keyword ExampleCreate a class named MyClass, with a property named x: class
MyClass: Try it Yourself » Create ObjectNow we can use the class named MyClass to create objects: ExampleCreate an object named p1, and print the value of x: p1 = MyClass() Try it Yourself » The __init__() FunctionThe examples above are classes and objects in their simplest form, and are not really useful in real life applications. To understand the meaning of classes we have to understand the built-in __init__() function. All classes have a function called __init__(), which is always executed when the class is being initiated. Use the __init__() function to assign values to object properties, or other operations that are necessary to do when the object is being created: ExampleCreate a class named Person, use the __init__() function to assign values for name and age: class Person: p1 = Person("John", 36) print(p1.name) Try it Yourself » Note:
The The __str__() FunctionThe __str__() function controls what should be returned when the class object is represented as a string. If the __str__() function is not set, the string representation of the object is returned: ExampleThe string representation of an object WITHOUT the __str__() function: class Person: p1 = Person("John", 36) print(p1) Try it Yourself » ExampleThe string representation of an object WITH the __str__() function: class Person: def __str__(self): p1 = Person("John", 36) print(p1) Try it Yourself » Object MethodsObjects can also contain methods. Methods in objects are functions that belong to the object. Let us create a method in the Person class: ExampleInsert a function that prints a greeting, and execute it on the p1 object: class Person: def myfunc(self): p1 = Person("John", 36) Try it Yourself » Note:
The The self ParameterThe It does not have to be named ExampleUse the words mysillyobject and abc instead of self: class Person: def myfunc(abc): p1 = Person("John", 36) Try it Yourself » Modify Object PropertiesYou can modify properties on objects like this: Delete Object PropertiesYou can delete properties on objects by using the Delete ObjectsYou can delete objects by using the The pass Statement
Test Yourself With ExercisesPython Objects and ClassesPython is an object-oriented programming language. Unlike procedure-oriented programming, where the main emphasis is on functions, object-oriented programming stresses on objects. An object is simply a collection of data (variables) and methods (functions) that act on those data. Similarly, a class is a blueprint for that object. We can think of a class as a sketch (prototype) of a house. It contains all the details about the floors, doors, windows, etc. Based on these descriptions we build the house. House is the object. As many houses can be made from a house's blueprint, we can create many objects from a class. An object is also called an instance of a class and the process of creating this object is called instantiation. Defining a Class in PythonLike function definitions begin with the def keyword in Python, class definitions begin with a class keyword. The first string inside the class is called docstring and has a brief description of the class. Although not mandatory, this is highly recommended. Here is a simple class definition.
A class creates a new local namespace where all its attributes are defined. Attributes may be data or functions. There are also special attributes in it that begins with double underscores As soon as we define a class, a new class object is created with the same name. This class object allows us to access the different attributes as well as to instantiate new objects of that class.
Output 10 <function Person.greet at 0x7fc78c6e8160> This is a person class Creating an Object in PythonWe saw that the class object could be used to access different attributes. It can also be used to create new object instances (instantiation) of that class. The procedure to create an object is similar to a function call.
This will create a new object instance named harry. We can access the attributes of objects using the object name prefix. Attributes may be data or method. Methods of an object are corresponding functions of that class. This means to say, since
Output <function Person.greet at 0x7fd288e4e160> <bound method Person.greet of <__main__.Person object at 0x7fd288e9fa30>> Hello You may have noticed the This is because, whenever an object calls its method, the object itself is passed as the first argument. So, In general, calling a method with a list of n arguments is equivalent to calling the corresponding function with an argument list that is created by inserting the method's object before the first argument. For these reasons, the first argument of the function in class must be the object itself. This is conventionally called self. It can be named otherwise but we highly recommend to follow the convention. Now you must be familiar with class object, instance object, function object, method object and their differences. Constructors in PythonClass functions that begin with double underscore Of one particular interest is the This type of function is also called constructors in Object Oriented Programming (OOP). We normally use it to initialize all the variables.
Output 2+3j (5, 0, 10) Traceback (most recent call last): File "<string>", line 27, in <module> print(num1.attr) AttributeError: 'ComplexNumber' object has no attribute 'attr' In the above example, we defined a new class to represent complex numbers. It has two functions, An interesting thing to note in the above step is that attributes of an object can be created on the fly. We created a new attribute attr for object num2 and read it as well. But this does not create that attribute for object num1. Deleting Attributes and ObjectsAny attribute of an object can be deleted anytime, using the
We can even delete the object itself, using the del statement.
Actually, it is more complicated than that. When we do On the command This automatic destruction of unreferenced objects in Python is also called garbage collection. Deleting objects in Python removes the name bindingWhat are the types of classes in Python?Python | Set 3 (Strings, Lists, Tuples, Iterations). Python String.. Python Lists.. Python Tuples.. Python Sets.. Python Dictionary.. Python Arrays.. What is class function method in Python?The classmethod() is an inbuilt function in Python, which returns a class method for a given function.; Syntax: classmethod(function) Parameter :This function accepts the function name as a parameter. Return Type:This function returns the converted class method.
What is __ init __ function in classes?The __init__ method is the Python equivalent of the C++ constructor in an object-oriented approach. The __init__ function is called every time an object is created from a class. The __init__ method lets the class initialize the object's attributes and serves no other purpose. It is only used within classes.
What are classes and functions?Classes are used to define the operations supported by a particular class of objects (its instances). If your application needs to keep track of people, then Person is probably a class; the instances of this class represent particular people you are tracking. Functions are for calculating things.
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