python魔方方法

正确代码

class Data:
    def __init__(self,number):
        self.number = number
        
    #注意other和self.number顺序不能乱
    def __add__(self,other):
        return other + self.number

if __name__ == '__main__':
    number1 = Data(30)
    number2 = Data(20)
    print(number1 + number2)

[root@master python]# python3 test.py 
50

错误代码

class Data:
    def __init__(self,number):
        self.number = number
           
    def __add__(self,other):
        return self.number + other

if __name__ == '__main__':
    number1 = Data(30)
    number2 = Data(20)
    print(number1 + number2)

[root@master python]# python3 test.py 
Traceback (most recent call last):
  File "test.py", line 43, in 
    print(number1 + number2)
  File "test.py", line 32, in __add__
    return self.number + other
TypeError: unsupported operand type(s) for +: 'int' and 'Data'

cat iter.py 
#!/usr/bin/env python
#coding: utf-8
class Data:
    def __init__(self,role_items):
         self.role_items = role_items
    def __iter__(self):
        for i in self.role_items:
            yield i


    def __radd__(self,other):
        return other+list(self)
    
    def test(self):
       return Data([role_items])

role=[1,2,3]
data=Data(role)
print(data)
for i in data:
    print(i)

python3 iter.py 
<__main__.Data object at 0x7f2f09f084e0>
1
2
3

cat iter.py 
#!/usr/bin/env python
#coding: utf-8
class Data:
    def __init__(self,role_items):
         self.role_items = role_items
    def __iter__(self):
        for i in self.role_items:
            yield i


    def __radd__(self,other):
        return other+list(self)
    
    def test(self):
       return Data([role_items])

role=[1,2,3]
data=Data(role)
#print(data)
#for i in data:
#    print(i)
list1=[4,5,6]
print(list1+data)

python3 iter.py 
[4, 5, 6, 1, 2, 3]