什么是运算符重载 python

Question

什么是运算符重载 python

Answer 1

example (Buffer support << , Fee support + / +=)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

#!/usr/bin/env python # coding: utf-8   class Buffer(object):     def __init__(self):         self.buffer = []           def __lshift__(self, data):         self.buffer.append(data)         return self           def __str__(self):         return repr(self.buffer)     class Fee(object):     def __init__(self, qty=0, amount=0):         self.qty = qty         self.amount = amount           def __radd__(self, another):         return self if not another else self + another           def __add__(self, another):         return Fee(             qty=self.qty + another.qty,             amount=self.amount + another.amount             )           def __repr__(self):         return "%s(%s)" % (             self.__class__.__name__,             ', '.join([                 '%s=%r' % item                  for item in self.__dict__.items()                 ])             )     def tester():     buff = Buffer()     buff << Fee(1, 23.5) << Fee(23, 1023.23)     print sum(buff.buffer)     if __name__ == "__main__":     tester()

 

Answer 2

自定义类在+右边的时候，需要定义 __radd__(self, other) 方法。如果左侧的obj没有定义__add__，那么python会自动调用右侧obj的__radd__。
其它运算符也是这样的。都是前面加个r表示右侧，例如__rmul__

Answer 3

class indexer:
def __getitem__(self, index): #iter override
return index ** 2
X = indexer()
X[2]
for i in range(5):
print X[i]