[Python-ideas] Vectorization [was Re: Add list.join() please]

[Kirill Balunov]

вс, 3 февр. 2019 г. в 21:23, David Mertz <mertz at gnosis.cx>:

>
> I think the principled thing to do here is add the minimal number of
> methods to Vector itself, and have everything else pass through as
> vectorized calls.  Most of that minimal number are "magic method":
> __len__(), __contains__(), __str__(), __repr__(), __iter__(),
> __reversed__().  I might have forgotten a couple.  All of those should not
> be called directly, normally, but act as magic for operators or built-in
> functions.
>
> I think I should then create regular methods of the same name that perform
> the vectorized version.  So we would have:
>
> len(v)   # -> 12
>
> v.len()  # -> <Vector of [3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3]>
>
> list(v)  # -> ["Jan", "Feb", "Mar", "Apr", "May", "Jul" ...]
> v.list() # -> <Vector of [["J", "a", "n"], ["F", "e", "b"] ... >
>
>
>
Hi David! Thank you for taking the time to implement this idea. Sorry, I'm
on a trip now and can't try it. From what I've read in this thread, I think
I mostly agree with your perception how the vector should work: that `len(v)
 # -> 12` and that `.some_method()` call must apply to elements (although
pedants may argue that in this case there is not much difference). The only
moment that I don’t like is `v.len(), v.list() and ...`, for the same
reasons -  in general this will not work. I also don't like the option with
`.apply` - what if `.apply` method is already defined for elements in a
vector?


> I can't implement every single constructor that users might
> conceivably want, of course, but I can do it for the basic types in
> builtins and common standard library.  E.g. I might do:
>
> v.deque() # -> <Vector of [deque(["J", "a", "n"]), deque(["F", "e", "b"])
> ... >
>
>
> But I certainly won't manually add:
>
> v.custom_linked_list()  # From my_inhouse_module.py
>
>
> Hmm... maybe even I could look at names of maybe-constructors in the
> current namespace and try them.  That starts to feel too magic.  Falling
> back to this feels better:
>
> map(custom_linked_list, v)  # From my_inhouse_module.py
>
>
>
Actually my thoughts on this. At first I thought that for these purposes it
is possible to use __call__:

len(v)   # -> 12

v(len)   # -> <Vector of [3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3]>


But it somehow this idea did not fit in my head. Then I found the next way
and I think I even like it - to reuse the `__getitem__`, when its argument
is a function it means that you apply this function to every element in the
vector.

len(v)   # -> 12

v[len]   # -> <Vector of [3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3]>


In this case you can apply any function, even custom_linked_list from
my_inhouse_module.py. From this stream I did not understand what desired
behavior for unary operations like `vector + 1` and  the others. Also what
is the desired behaviour for `vector[1:5]`? Considering the above, I would
like to take this operation on the contrary:

>>> v
<Vector of ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep',
'Oct', 'Nov', 'Dec']>
>>> v[1:]
<Vector of ['Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct',
'Nov', 'Dec']>
>>> v[i[1:]] # some helper class `i`
<Vector of ['an', 'eb', 'ar', 'pr', 'ay', 'un', 'ul', 'ug', 'ep', 'ct',
'ov', 'ec']>

With kind regards,
-gdg
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