[learn Python from simple to deep] definition and use of object-oriented class 1

1. Classes and objects ：

（1） Class is a general term for something , The object is a real object . for example ： Animals are a class , Dogs and cats are objects .
（2） Class through instantiation , Get the object

2. The definition of a class ：

（1） Class has properties and methods
（2）__init__ Method is a special method , Every time you create an object with a class , Will automatically run this method .
The name of the method , There are two underscores at the beginning and two underscores at the end , It's an agreement , Avoid conflicts with other common method names
（3） Parameters self Is a reference to the object itself , Whether the object can access the properties and methods in the class .
self It is an automatic transfer without manual transfer , So when creating objects from classes , Just give the following formal parameters （name,age） Provide value .

# Defining classes 
class Animal:
# Define the properties of the class ： By construction method 
def __init__(self,name,age):
self.name=name
self.age=age
# Define the methods of the class 
def sit(self):
# Simulate the animal being ordered to sit down 
print(self.name + " is now sitting")

# Instantiation 1—— Get objects through classes 
dog=Animal('Xiaohua',3)

print(dog.name)
print(dog.age)

Xiaohua
3

# Instantiation 2—— Get other objects 
cat=Animal('Xiaomao',2)

cat.name

‘Xiaomao’

cat.sit()

Xiaomao is now sitting