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1989922yan
V2EX  ›  Python

len()在类中有什么特殊方法? len()一个实例,是 len 了什么的长度呢?

  •  
  •   1989922yan · Dec 2, 2014 · 3792 views
    This topic created in 4315 days ago, the information mentioned may be changed or developed.
    >>> class A(dict): pass
    >>> aa = A()
    >>> len(aa)

    len()在类中有什么特殊方法? len()一个实例,是 len 了什么的长度呢?
    4 replies  •  2014-12-02 16:32:47 +08:00
    lianghui
        1
    lianghui  
       Dec 2, 2014   ❤️ 2
    __len__ 方法
    aheadlead
        2
    aheadlead  
       Dec 2, 2014   ❤️ 1
    1L正解...
    staticor
        3
    staticor  
       Dec 2, 2014   ❤️ 1
    可参考http://stackoverflow.com/questions/2481421/difference-between-len-and-len 或者定义一个类后改写一下 __len__ 方法
    joshryo
        4
    joshryo  
       Dec 2, 2014   ❤️ 1
    len函数会去调用类的__len__方法,所以想要能用len函数,你定义类的时候都得写__len__方法
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