Why People Should Learn Python

Re:Why People Should Learn Python by perlgeek on Wednesday August 24, 2016 @11:47AM (#12352875)

The second annoyance is that you need to write __init__ methods quite often.

Correct me if I'm wrong, but there doesn't seem to be built-in support in Python for having attributes initialized by the the constructor.

For example in Perl 6, I can write

    class Point {
        has $.x;
        has $.y;
    }

... and I get a constructor Pair.new(x => 1, y => 42) for free, no need to write custom initializers.

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Re:Why People Should Learn Python by squeaky-clean on Wednesday August 24, 2016 @04:11PM (#12354864)

Nothing built in, and generally not recommended, but you can do it! If you want to be really flexible and just allow any attribute, you can do this:

    class Foo:
      def __init__(self, *args, **kwargs):
        self.__dict__.update(**kwargs)

And it will automatically assign any keyword arguments you use as attributes to the object. For example `foo = Foo(name='Bob', age=99)`

If you still want to keep a strict list of allowed attributes, you can define them as parameters, and use a shortcut to assign all local variables to attributes.

    class Foo:
      def __init__(self, name, age):
        self.__dict__.update(locals())
        del self.self

So `foo = Foo(name='Bob', age=99)` will still work as will `foo = Foo('Bob', 99)`. But `foo = Foo('Bob', 99, True)` will throw an error, as will `foo = Foo(name='Bob', age=99, likes_cake=True)`. You can add kwargs back to the parameter list if you want to allow assigning any attribute.

This isn't recommended though. So for all practical purposes, Python does require a bit of boilerplate in the constructor.

Edit: Realized a cleaner way to do the second example.

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Re:Why People Should Learn Python by amyjess on Friday August 26, 2016 @10:02AM (#12366300)

I believe you could also accomplish this with a metaclass, as well.

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