对python 中class与变量的使用方法详解

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。

#!/usr/bin/python
#encoding:utf-8

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

简单的写了个测试小程序，枚举了各种情况，没有办法全部枚举，但大部分情况应该都已经包含了。

1. 类变量：能够通过类名或者object的self来访问到，在类的内部和外部均可达，比如class_var_1

2. 对象变量：可以通过对象的self来使用的变量，通过constructor一路走向去的的self初次被赋值的变量都会成为对象变量，比如object_var_1, object_var_2, object_var_3, object_var_4

3. 内部变量：可以在函数中定义，并加上self前缀，在初次调用过定义的函数后，就可以在后面的对象的函数中被使用，比如internal_var_1

4. 局部变量：在函数内部定义，并使用的变量，在使用完之后就会被回收对类及object不可见

5. 全局变量：定义在类或者函数外部，作用域在变量被定义之后的任意代码段，比如：global_var_1

以上是基于我自己的测试得到的结论，如果有不对的地方，可以帮忙指正。

这篇对python 中class与变量的使用方法详解就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持脚本之家。

来源：https://blog.csdn.net/lwc5411117/article/details/83546759