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原因是多写了一个print，d.met()就足够了（其中已经print了）
多写的那个print首先执行了d.met()，然后打印了调用d.met()的返回值，就是"None"。注意："D.met"是d.met()打印的

On 12/7/06, leopay <leopay at gmail.com> wrote:
>
>  class A(object):
>     def met(self):
>         print 'A.met'
> class B(A):
>     def met(self):
>         print 'B.met'
>
> class C(A):
>     def met(self):
>         print 'C.met'
>
> class D(B,C):
>     def met(self):
>         print 'D.met'
>
> d=D()
> print d.met()
>
> D.met
> None
>
> 请问这个None是怎么来的？
>
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> python-chinese
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On 12/7/06, leopay <leopay在gmail.com> wrote:
>
>  class A(object):
>      def met(self):
>          print 'A.met'
>  class B(A):
>      def met(self):
>          print 'B.met'
>
>  class C(A):
>      def met(self):
>          print 'C.met'
>
>  class D(B,C):
>      def met(self):
>          print 'D.met'
>
>  d=D()
>  print d.met()
>
>  D.met
>  None
>
>  请问这个None是怎么来的？
>
当一个函数没有return时，它返回一个None


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不好意思，犯了个低级错误

Bing Yuan 写道:
> 原因是多写了一个print，d.met()就足够了（其中已经print了）
> 多写的那个print首先执行了d.met()，然后打印了调用d.met()的返回值，就是
> "None"。注意："D.met"是d.met()打印的
>
> On 12/7/06, *leopay* < leopay在gmail.com leopay在gmail.com>> wrote:
>
>     class A(object):
>     def met(self):
>     print 'A.met'
>     class B(A):
>     def met(self):
>     print 'B.met'
>
>     class C(A):
>     def met(self):
>     print 'C.met'
>
>     class D(B,C):
>     def met(self):
>     print 'D.met'
>
>     d=D()
>     print d.met()
>
>     D.met
>     None
>
>     请问这个None是怎么来的？
>
>     _______________________________________________
>     python-chinese
>     Post: send python-chinese在lists.python.cn
>     python-chinese在lists.python.cn>
>     Subscribe: send subscribe to
>     python-chinese-request在lists.python.cn
>     python-chinese-request在lists.python.cn>
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>     python-chinese-request在lists.python.cn
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>
> ------------------------------------------------------------------------
>
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