1、while for 增加了循环正常结束后执行的else代码块。
2、Objects are mutable
3、import copy
p1 = Point()
p2=copy.copy(p1) # this operation is called a shallow copy because it copies the object and any references it contains, but not the embedded objects.
p3=copy.deepcopy(box) # deepcopy copies not only the object but aslo the objects it refers to.
p1 is p2 False
p1 == p2 False
the default behavior of the == operator is the same as the is operator; it checks object identify, not object equivalence.
4、if you try to access an attribute that doesnot exist, you get an AttributeError
type(p)
isinstance(p, Point)
hasattr(p, 'x')