python操作符重寫，實現+操作符

import string
class spam:
    def init(self):
        self.eggs = 1
    def del(self):
        pass
    def add(self,other):
         rt = spam()
         rt.eggs = self.eggs + other.eggs
         return rt
    def coerce(self,other):
         rt = spam()
         if type(other) == type(rt):
             return (self,other)
         elif type(other) == type(''):
             e = string.atoi(other)
             rt.eggs = e
             return(self,rt)
         else:
             return None
    def radd(self,other):
         return self + other

if name == 'main':
     a = spam()
     b = spam()
     a = a + b
     print 'a now has', a.eggs, 'eggs'
     a = a + '24'
     print 'a now has', a.eggs, 'eggs'
     a = '24' + a
     print 'a now has', a.eggs, 'eggs'
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