在派生类上调用 __coerce__() 方法会导致错误
我的试验如下，但没有成功。
class MyNum:
def __init__(self , n):
self.n = n
class MyNum2(MyNum):
def __coerce__(self , y):
return self, y
def __radd__(self, y):
print 'radd called'
return self.n + y.n
我在 python 命令行中输入：
>>> x = MyNum(20)
>>> y = MyNum2(12)
>>> x+y
结果：
>>> Traceback (most recent call last):
File "", line 1, in
y+x
File "", line 3, in __coerce__
return self.y
AttributeError: MyNum instance has no attribute 'y'
当我使用 __coerce__() 方法而不进行类派生时，结果为 x+y 等于 radd 调用 // 32。但是，对于派生类，会发生错误。
请给我一些帮助，祝农历新年快乐，提前谢谢。
My trial was like below, but it didn't work.
class MyNum:
def __init__(self , n):
self.n = n
class MyNum2(MyNum):
def __coerce__(self , y):
return self, y
def __radd__(self, y):
print 'radd called'
return self.n + y.n
I typed on the python command line:
>>> x = MyNum(20)
>>> y = MyNum2(12)
>>> x+y
Result:
>>> Traceback (most recent call last):
File "", line 1, in
y+x
File "", line 3, in __coerce__
return self.y
AttributeError: MyNum instance has no attribute 'y'
When I use the __coerce__() method without class deriving, the result ofx+y equals to radd called // 32. However, with derived-class, an error occurs.
Please give me some help, and happy lunar new year, thank you in advance.
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评论（1）
根据错误消息，您的 __coerce__ 实现实际上具有
而不是
您在示例代码中编写的内容。
上面的代码对我有用，实际上您甚至不需要这里的 __coerce__ 方法。在您的示例中，只需使用
__radd__就足够了。Based on the error message, your
__coerce__implementation actually hadinstead of the
as you've written in the example code.
Your code above works for me, and you don't actually even need the
__coerce__method here. Just having the__radd__is sufficient in your example.