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Python inheritance: combining with super __str__

I want the child class __str__

implementation to be added to the base implementation:

class A:
    def __str__(self):
        return "this"

class B(A):
    def __str__(self):
        return super(B, self) + " + that"

This, however, creates an error like:

TypeError: unsupported operand type for +: 'super' and 'str'

Is there a way to get a str(B())

return "this + that"

?

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4 answers


You need to do super(B, self).__str__()

. super

refers to the parent class; you don't call any methods.



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For python 2, like others posted.

class A(object):
    def __str__(self):
        return "this"

class B(A):
    def __str__(self):
        return super(B, self).__str__() + " + that"


For python 3, the syntax is simplified. super

does not require the arguments to work correctly.

class A():
    def __str__(self):
        return "this"

class B(A):
    def __str__(self):
        return super().__str__() + " + that"
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class B should be:

class B(A):
def __str__(self):
    return super(B, self).__str__() + ' + that
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Here's some working code. You needed

1) a subclass object, so super works as expected and

2) Use __str__()

when concatenating your string.

class A(object):
  def __str__(self):
    return "this"


class B(A):

  def __str__(self):
    return super(B, self).__str__() + " + that"

print B()

Note: print B()

calls b.__str__()

under the hood.

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