how to pass arguments efficiently (**kwargs in python)

Question

I have a class that inherits from 2 other classes. These are the base classes:

class FirstBase(object):
      def __init__(self, detail_text=desc, backed_object=backed_object,
                   window=window, droppable_zone_obj=droppable_zone_obj,
                   bound_zone_obj=bound_zone_object,
                   on_drag_opacity=on_drag_opacity):
          # bla bla bla

class SecondBase(object):
      def __init__(self, size, texture, desc, backed_object, window):
          # bla bla bla

And this is the child:

class Child(FirstBase, SecondBase):
       """ this contructor doesnt work
       def __init__(self, **kwargs):
          # PROBLEM HERE
          #super(Child, self).__init__(**kwargs)
       """
       #have to do it this TERRIBLE WAY
       def __init__(self, size=(0,0), texture=None, desc="", backed_object=None,
                    window=None, droppable_zone_obj=[], bound_zone_object=[],
                    on_drag_opacity=1.0):
          FirstBase.__init__(self, detail_text=desc, backed_object=backed_object,
                             window=window, droppable_zone_obj=droppable_zone_obj,
                             bound_zone_obj=bound_zone_object,
                             on_drag_opacity=on_drag_opacity)
          SecondBase.__init__(self, size, texture, desc, backed_object, window)

I wanted to solve it all nicely with **kwargs but when I call the first commented out constructor I get TypeError: __init__() got an unexpected keyword argument 'size'.

Any ideas how I can make it work with **kwargs?

Answer 1

您的问题是您只尝试super在子类中使用.

如果您super也在基类中使用,那么这将起作用.每个构造函数将"吃掉"它所采用的关键字参数,而不是将它们传递给下一个构造函数.object调用构造函数时,如果剩下任何关键字参数,则会引发异常.

class FirstBase(object):
    def __init__(self, detail_text=None, backed_object=None,
                 window=None, droppable_zone_obj=None,
                 bound_zone_obj=None, on_drag_opacity=None, **kwargs):
        super(FirstBase, self).__init__(**kwargs)

class SecondBase(object):
    def __init__(self, size=(0,0), texture=None, desc="",
                 backed_object=None, window=None, **kwargs):
        super(SecondBase, self).__init__(**kwargs)

class Child(FirstBase, SecondBase):
    def __init__(self, **kwargs):
        super(Child, self).__init__(**kwargs)

如您所见,它可以工作,除非您传递一个伪造的关键字参数:

>>> Child()
<__main__.Child object at 0x7f4aef413bd0>
>>> Child(detail_text="abc")
<__main__.Child object at 0x7f4aef413cd0>
>>> Child(bogus_kw=123)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "test.py", line 14, in __init__
    super(Child, self).__init__(**kwargs)
  File "test.py", line 5, in __init__
    super(FirstBase, self).__init__(**kwargs)
  File "test.py", line 10, in __init__
    super(SecondBase, self).__init__(**kwargs)
TypeError: object.__init__() takes no parameters