super() in Python 3
Hi there! A lot of the answers to your questions are at least implied
in the Fine Manual
(https://docs.python.org/3/library/functions.html#super), but it's not
very clear and written more for precision than comprehension. Here's my
attempt at explaining :-)
On 16/07/2019 11:08, ???? wrote:
> 1. When we use super() in Python 3, we don't pass it the first argument
> (self). Why?
Actually the first argument to super() isn't self, it's the class that
we want the superclass of. The *second* argument is self. In the
normal course of using super() inside a class method, these arguments
will almost always be the class itself and the instance the method was
called on. Since that's almost always the case, the compiler offers us
a short-cut: omit the "cls" and "self" and the compiler will fill them
in for us. That way we don't have to repeat ourselves and risk
> What happens if the first argument is not self?
The first argument of what? I'm not sure what you're getting at here.
> I think it would make more sense to use something like
> self.super().__init__(*args, **kwargs) or something like this.
That would mean either forbidding classes to have a method named "super"
or accepting that users' classes could completely screw up inheritance
for their subclasses.
> 2. I want to override a function called build_suite in an inherited class.
> The function receives an argument "test_labels" which I want to change (I
> define it if it's not defined), but I don't do anything with the argument
> "extra_tests". Is it possible to include "extra_tests" in *args, **kwargs
> and how?
Don't list it in your parameters :-)
def build_suite(self, test_labels=None, *args, **kwargs):
return super().build_suite(test_labels=test_labels, *args, **kwargs)
> I think maybe they will release another version in the future
> without "extra_tests", or with additional arguments, and I don't want to
> have to change my code then.
With a shim layer like this, your chances of getting away with making no
changes to your code when an API you use changes are rather small.
Rhodri James *-* Kynesim Ltd