如何继承python生成器并覆盖__iter__

Question

我想打电话给母班,但我得到这样的信息:

Traceback (most recent call last):
  File "***test.py", line 23, in <module>
    for i in daughter:
  File "***test.py", line 18, in __iter__
    for i in super(Mother, self):
TypeError: 'super' object is not iterable

我认为这只是语法,我试着在没有任何方法的情况下调用超级(母亲,自己),只是对象本身.这里的代码:

class Mother(object):
    def __init__(self, upperBound):
        self.upperBound = upperBound

    def __iter__(self):
        for i in range (self.upperBound):
            yield i


class Daughter(Mother):
    def __init__(self, multiplier, upperBound):
        self.multiplier = multiplier
        super(Daughter, self).__init__(upperBound)

    def __iter__(self):
        for i in super(Mother, self): # Here
            yield i * self.multiplier


daughter = Daughter(2, 4)
for i in daughter:
    print i

这只是一个例子,我的目的是读取文件并逐行屈服.然后子类生成器解析所有行(例如,从行中生成一个列表...).

Answer 1

返回的代理对象super()是不可迭代的，因为__iter__MRO 中有一个方法。您需要明确查找此类方法，因为只有这样才会开始搜索：

for i in super(Daughter, self).__iter__():
    yield i * self.multiplier

请注意，您需要super()在当前类上使用，而不是在父类上使用。

super()不能直接支持特殊方法，因为这些方法是由 Python 直接在类型上查找的，而不是实例。请参阅新式类的特殊方法查找：

对于新式类，特殊方法的隐式调用只有在对象的类型上定义时才能保证正确工作，而不是在对象的实例字典中。

type(super(Daughter, self))是super类型对象本身，它没有任何特殊的方法。

演示：

>>> class Mother(object):
...     def __init__(self, upperBound):
...         self.upperBound = upperBound
...     def __iter__(self):
...         for i in range (self.upperBound):
...             yield i
...
>>> class Daughter(Mother):
...     def __init__(self, multiplier, upperBound):
...         self.multiplier = multiplier
...         super(Daughter, self).__init__(upperBound)
...     def __iter__(self):
...         for i in super(Daughter, self).__iter__():
...             yield i * self.multiplier
...
>>> daughter = Daughter(2, 4)
>>> for i in daughter:
...     print i
...
0
2
4
6