preface
We have already learned the basic data types, functions and file reading and writing in Python. Next, we will look at object-oriented programming in Python. If you have learned object-oriented programming language like Java, you will feel very easy to learn compared to Object-oriented programming in Python. Python is much simpler and more convenient in object-oriented terms than Java, with far fewer constraints.
Create an object
Python, like other languages, uses the class keyword to declare a class. The class name is humped and begins with a capital letter.
class Animal:
def __init__(self, name, age):
self.name = name
self.age = age
def run(self):
print(self.name + " is running")
Copy the code__init__()Methods are essential in order to instantiate objects
As shown in the code above, the __init__() method in the Pyhton class is essential for instantiating object initialization, somewhat similar to constructors in Java. Self is essential in the __init__() method and must come first, being a reference to itself.
Create an instance
Python instantiates objects in the following way, without using the new keyword.
class Animal:
def __init__(self, name, age):
self.name = name
self.age = age
def run(self):
print(self.name + " is running")
dog = Animal('lily', 2)
Copy the codeAccess properties and methods
Both properties and methods are directly accessible in Python
class Animal:
def __init__(self, name, age):
self.name = name
self.age = age
def run(self):
print(self.name + " is running")
dog = Animal('lily', 2)
print(dog.age)
print(dog.name)
dog.run()
Copy the codeAdd default values to properties
Python can set default values for properties so that no arguments are passed during initialization.
class Animal:
def __init__(self, age):
self.name = 'Lily'
self.age = age
def run(self):
print(self.name + " is running")
Copy the codeModifies the value of an attribute
Pyhton can modify the value of a property in two ways, first by directly accessing it.
class Animal:
def __init__(self, name, age):
self.name = name
self.age = age
def run(self):
print(self.name + " is running")
dog = Animal('lily', 2)
dog.name = 'Harry'
dog.age = 3
print(dog.age)
print(dog.name)
dog.run()
Copy the codeThe result is shown below
Property values can also be changed through methods, similar to setters in Java.
class Animal:
def __init__(self, name, age):
self.name = name
self.age = age
def run(self):
print(self.name + " is running")
def update_name(self, name):
self.name = name
Dog = Animal('Harry', 2)
Dog.update_name('Lily')
Dog.run()
Copy the codeInherit the parent class
Inheritance is also possible in Python, but instead of using the extends keyword, parentheses are used directly. Super ().__init__(name, age) ties the subclass to its parent class.
class Animal:
def __init__(self, name, age):
self.name = name
self.age = age
def run(self):
print(self.name + " is running")
class Dog(Animal):
def __init__(self, name, age, leg):
super().__init__(name, age)
self.leg = 4
Harry = Dog("Harry", 2, 4)
print(Harry.leg)
Copy the codeOverriding methods
Overriding is relatively simple in Python. If a subclass has a function with the same name as its parent, the subclass’s instance calls the function directly.
class Animal:
def __init__(self, name, age):
self.name = name
self.age = age
def run(self):
print(self.name + " is running")
def update_name(self, name):
self.name = name
class Dog(Animal):
def __init__(self, name, age, leg):
super().__init__(name, age)
self.leg = 4
def run(self):
print("Dog is running")
Harry = Dog("Harry", 2, 4)
Harry.run()
Copy the codeThe last
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