重新定义__and__运算符 [英] redefine __and__ operator

问题描述

为什么我不能重新定义__and__运算符?

Why I can't redefine the __and__ operator?

class Cut(object):
      def __init__(self, cut):
         self.cut = cut
      def __and__(self, other):
         return Cut("(" + self.cut + ") && (" + other.cut + ")")

a = Cut("a>0") 
b = Cut("b>0")
c = a and b
print c.cut()

我想要(a>0) && (b>0)，但是我得到了b，这是and

I want (a>0) && (b>0), but I got b, that the usual behaviour of and

推荐答案

__and__是二进制(按位)&运算符，而不是逻辑and运算符.

__and__ is the binary (bitwise) & operator, not the logical and operator.

由于and运算符是短路运算符，因此无法实现为函数.也就是说，如果第一个参数为false，则根本不评估第二个参数.如果您尝试将其实现为函数，则在调用该函数之前必须先对两个参数进行求值.

Because the and operator is a short-circuit operator, it can't be implemented as a function. That is, if the first argument is false, the second argument isn't evaluated at all. If you try to implement that as a function, both arguments have to be evaluated before the function can be invoked.

这篇关于重新定义__and__运算符的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！