%cat pytest1.py
class Dog:
    def __init__(self,x): self.zn = x
    def __getattr__(self,key): return key+' not found'
    def __add__ (self,x): self.zn += x; return self.zn
    def __radd__(self,x): self.zn += x; return self.zn
    def __sub__ (self,x): self.zn -= x; return self.zn
    def __rsub__(self,x): self.zn = x - self.zn; return self.zn
    def __mul__ (self,x): self.zn *= x; return self.zn
    def __truediv__ (self,x): self.zn /= x; return self.zn
    def __mod__ (self,x): self.zn = self.zn%x; return self.zn

dog = Dog(1.1)
print(dog + 1)
print(1 - dog)
print(dog * 4)
print(dog/2)
print(dog % 3)
print(dog.zn)
print(dog.y)

%python pytest1.py
2.1
-1.1
-4.4
-2.2
0.7999999999999998
0.7999999999999998
y not found

class MyClass:
    def __getitem__(self,key):
        return getattr(self, key)
    def __setitem__(self,key,value):
        return setattr(self, key, value)
A = MyClass()
A['name']='alex'
print(A['name'])
# °á°ú
alex