init in overridden classmethod

Question

I have a small class hierarchy with similar methods and __init__(), but slightly different static (class) read() methods. Specifically will the child class need to prepare the file name a bit before reading (but the reading itself is the same):

class Foo: def __init__(self, pars): self.pars = pars @classmethod def read(cls, fname): pars = some_method_to_read_the_file(fname) return cls(pars) class Bar(Foo): @classmethod def read(cls, fname): fname0 = somehow_prepare_filename(fname) return cls.__base__.read(fname0)

The problem here is that Bar.read(…) returns a Foo object, not a Bar object. How can I change the code so that an object of the correct class is returned?

Does this answer your question? What does 'super' do in Python? - difference between super().__init__() and explicit superclass __init__() — matszwecja
– matszwecja, Commented Dec 5, 2023 at 9:37
Does this answer your question? Using super with a class method — ivvija
– ivvija, Commented Dec 5, 2023 at 9:39

blhsing · Accepted Answer · 2023-12-05 09:37:49Z

cls.__base__.read binds the read method explicitly to the base class. You should use super().read instead to bind the read method of the parent class to the current class.

Change:

return cls.__base__.read(fname0)

to:

return super().read(fname0)

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