C++中的虚函数与多态，是很多C++面向对象程序设计的一个基础，在Python中，是否也存在多态和虚函数，答案是有的。看下面的这个例子
[python] view plain copyfrom abc import ABCMeta, abstractmethod
class Base():
__metaclass__ = ABCMeta
def __init__(self):
pass
@abstractmethod
def get(self):
print "Base.get()"
pass
class Derive1(Base):
def get(self):
print "Derive1.get()"
class Derive2(Base):
def get(self):
print "Derive2.get()"
if name == '__main__':
b = Base()
b.get()
运行的时候，提示：
b = Base()
TypeError: Can't instantiate abstract class Base with abstract methods get
如果分别构建两个子类的对象，则
[python] view plain copyif name == '__main__':
b = Derive1()
c = Derive2()
b.get()
c.get()
运行结果：Derive1.get()Derive2.get()
从上面的例子可以看出，代码已经具备C++中多态和虚函数的特点了
那么，Python是如何做到这点的？
1.abc module
在代码中，首先
[python] view plain copyfrom abc import ABCMeta, abstractmethod python 文档对于abc是这么定义的This module provides the infrastructure for defining abstract base classes (ABCs) in Python
声明 metaclass
[python] view plain copymetaclass = ABCMeta Use this metaclass to create an ABC. An ABC can be subclassed directly, and then acts as a mix-in class
关于metaclass的定义，可以参见http://jianpx.iteye.com/blog/908121
3.申明函数为虚函数
[python] view plain copy@abstractmethod
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