#头条创作挑战赛#

目录：

面向对象编程，类的定义，类的属性，类方法，__init__ 初始化魔法方法

类的概述

1. 类是对数据和函数的封装。
2. 创建一个类就是创建了一个新的数据类型。
3. 类的实例通过属性来显示它的状态。

学习目录

1 什么是类

2 类的定义

2.1 类属性

2.2类方法

python中的变量定义是很灵活的，很容易搞混淆，特别是对于class的变量的定义，如何定义使用类里的变量是我们维护代码和保证代码稳定性的关键。

 global_variable_1 = 'global_variable'
 
class MyClass():
  class_var_1 = 'class_val_1' # define class variable here
  def __init__(self, param):
    self.object_var_1 = param # define object variable here
    self.object_var_2 = 'object_val_2' # define object variable here
    self.object_func3()
 
  def object_func1(self, param):
    local_var_1 = param # define lcoal variable here
    local_var_2 = 'local_val_2' # define local variable here
    self.internal_var_1 = 'internal_val_1' # define internal variable here
    print(local_var_1) # we can use local variable of current here
    print(local_var_2) # we can use local variable of current here
    print(MyClass.class_var_1) # we can use class variable here, but you have using class name ass prefix
    print(self.class_var_1) # we can use class variable as object variable here
    print(self.object_var_1) # we can use object variable here
    print(self.object_var_2) # we can use object variable here
    print(self.internal_var_1) # we can use internal variable here
    #print(local_var_3) # we can't use local variable in another function
    print(global_variable_1) # we can use global variable here
 
  def object_func2(self, param='func_val_1'):
    local_var_3 = param # define local variable here
    print(local_var_3) # we can use lcoal variable here
    print(self.internal_var_1) # we can use internal variable defined in class_func1, but you have to call class_func1 first
    print(MyClass.class_var_1) # we can use class variable here, but you have using class name ass prefix
    print(self.class_var_1) # we can class variable here
    print(self.object_var_1) # we can use object variable here
    print(self.object_var_2) # we can use object variable here
    print(global_variable_1) # we can use global variable here
 
 
  def object_func3(self, param='func_val_1'):
    self.object_var_3 = param # because this function called in construction function, so this is defined as object variable, not internal variable
    self.object_var_4 = 'object_val_4' # because this function called in construction function, so this is defined as object variable, not internal variable
    print(global_variable_1) # we can use global variable here
  
  # define class function
  def class_func4():
    print(MyClass.class_var_1)
    print(global_variable_1) # we can use global variable here
 
if __name__ == '__main__':
  myObject = MyClass('object_val_1')
  print(MyClass.class_var_1) # we can use class variable directly here
  #print(MyClass.object_var_1) # we can't use object variable here
  print(myObject.object_var_1) # we can use object variable here
  print(myObject.object_var_2) # we can use object variable here
  print(myObject.object_var_3) # we can use object variable here
  print(myObject.object_var_4) # we can use object variable here
  #print(myObject.internal_var_1) # we can't use internal variable as object variable here
  MyClass.class_func4() # we can use class function here
  #MyClass.object_func2(myObject, 'local_var_3') # internal variable can't be used in this function
  myObject.object_func1('local_var_1') # call first function
  myObject.object_func2('local_var_3') # call second function
  print(global_variable_1) # we can use global variable here

介绍

Python 3.7 中有一个新特性, 你可以使用一个装饰器 @dataclass来简化创建数据类的过程，新创建的数据类将自带有__init__和__repr__。

数据类是一种用来存储数据的类，这种类往往不需要自定义的方法。通常，我们也管它叫数据结构。例如，一个存储点的三维坐标值的类，往往就只需要三个字段 (x, y, z)。