On 16/07/19 09:18, Chris Angelico wrote: > On Tue, Jul 16, 2019 at 3:32 PM Ian Kelly <ian.g.ke...@gmail.com> wrote: >> On Sun, Jul 14, 2019 at 7:14 PM Chris Angelico <ros...@gmail.com> wrote: >>> On Mon, Jul 15, 2019 at 10:51 AM Paulo da Silva >>> <p_s_d_a_s_i_l_v_a...@netcabo.pt> wrote: >>>> Às 15:30 de 12/07/19, Thomas Jollans escreveu: >>>>> On 12/07/2019 16.12, Paulo da Silva wrote: >>>>>> Hi all! >>>>>> >>>>>> Is there any difference between using the base class name or super to >>>>>> call __init__ from base class? >>>>> There is, when multiple inheritance is involved. super() can call >>>>> different 'branches' of the inheritance tree if necessary. >>>>> ... >>>> Thank you Jollans. I forgot multiple inheritance. I never needed it in >>>> python, so far. >>>> >>> Something to consider is that super() becomes useful even if someone >>> else uses MI involving your class. Using super() ensures that your >>> class will play nicely in someone else's hierarchy, not just your own. >> Just using super() is not enough. You need to take steps if you want to >> ensure that you class plays nicely with MI. For example, consider the >> following: >> >> class C1: >> def __init__(self, name): >> self._name = name >> >> class C2(C1): >> def __init__(self, name, value): >> super().__init__(name) >> self._value = value >> >> This usage of super is just fine for the single-inheritance shown here. But >> there are two reasons why this cannot be neatly pulled into an MI >> hierarchy. Can you spot both of them? > Well, obviously it's violating LSP by changing the signature of > __init__, which means that you have to be aware of its position in the > hierarchy. If you want things to move around smoothly, you HAVE to > maintain a constant signature (which might mean using *args and/or > **kwargs cooperatively).
I guess the second problem is that C1 doesn't call super. Meaning that if someone else uses this in a multiple heritance scheme, and the MRO reaches C1, the call doesn't get propagated to the rest. -- Antoon Pardon -- https://mail.python.org/mailman/listinfo/python-list
