Issue with inherited attributes in a class with multiple base classes

Question

EDIT: Thanks for the information about the class attributes. I understand these are similar to static in other OO languages. Now in the following code, I wish to use the __init__ of the base classes to set x and y in the derived class. Any guidance would be appreciated.

class Base1:
  def __init__(self, x):
      self.x = x

class Base2:
  def __init__(self, y):
      self.y = y

class Derv (Base1, Base2):
  def __init__(self, x, y):
      self.x = x
      self.y = y

OLD:

Related to Multiple inheritance: The derived class gets attributes from one base class only?

Now, what is happening in the following example (dictionary of d is empty):

class Base1:
  x = 10

class Base2:
  y = 10

class Derv (Base1, Base2):
  pass


d=Derv()
print (d.__dict__)

Although this works when we change the code to following:

class Base1:
  x = 0
  def __init__(self, x):
      self.x = x

class Base2:
  y = 0
  def __init__(self, y):
      self.y = y

class Derv (Base1, Base2):
  def __init__(self, x, y):
      self.x = x
      self.y = y

I think this is more because of defining x and y in the __init__ method of Derv. But, if I wish to set the values using base class constructors, what is the correct way?

Your two base classes both have a class attribute and an instance attribute with the same name—which is just asking for trouble. — martineau, Oct 24 '18 at 01:01
@Martineau. Exacerbated by the fact that OP isn't using parent constructors properly. — Mad Physicist, Oct 24 '18 at 01:15
Actually, I was looking for the correct syntax to invoke the base class constructors. — Yelena, Oct 24 '18 at 01:25

score 2 · Accepted Answer · answered Oct 24 '18 at 01:15

2

Easiest and best: just call the initializers in each base!

class Derv(Base1, Base2):
    def __init__(self, x, y):
        Base1.__init__(self, x)
        Base2.__init__(self, y)

answered Oct 24 '18 at 01:15

wim

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Thank you so much, that's what I was looking for. Tried using super().__init__(), but couldn't get the required results. – Yelena Oct 24 '18 at 01:23

Issue with inherited attributes in a class with multiple base classes

1 Answers1