python的新式类是2.2版本引进来的，我们可以将之前的类叫做经典类或者旧类。为什么要在2.2中引进new style class呢？官方给的解释是：

为了统一类(class)和类型(type)

In [1]: class A():
   ...:     a = 1
   ...:

In [2]: class B(object):
   ...:     b = 2
   ...:

In [3]: a = A()

In [4]: b = B()

In [5]: type(a)
Out[5]: instance

In [6]: type(b)
Out[6]: __main__.B

In [7]: a.__class__
Out[7]: <class __main__.A at 0x10ef22668>

In [8]: b.__class__
Out[8]: __main__.B

继承的搜索顺序

继承搜索的顺序发生了改变,经典类多继承属性搜索顺序: 先深入继承树左侧，再返回，开始找右侧;新式类多继承属性搜索顺序: 先水平搜索，然后再向上移动

slots

新式类新增slots属性，可以限制类的属性和方法

In [1]: class Person(object):
   ...:     __slots__ = ('name','age')
   ...:

In [2]: p = Person()

In [3]: p.name = 'FangHao'

In [4]: p.age = 24

In [5]: p.weigth = 150
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-5-0b75d36f0341> in <module>()
----> 1 p.weigth = 150

AttributeError: 'Person' object has no attribute 'weigth'

pyhton2.x 默认都是旧式类，除非显示的继承object
python3.x 默认都是新式类，隐式的继承object