python sentence

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')