Additions to the .rx namespace

[philippjfr]

As we have started building applications with rx a few gaps have become clear, specifically the following functionality is currently missing:

• Allow constructing "empty" rx() which initializes with a None value
• Currently there is no way to get the equivalent to the not keyword, therefore we introduce .rx.not_
• It is quite awkward to apply a function to each item in an iterable, therefore we introduce .rx.map
• Currently there is no way to achieve equivalent to the and keyword, therefore we introduce .rx.and_
• Currently there is no way to achieve equivalent to the or keyword, therefore we introduce .rx.or_
• Add support for an initial value on .param.when so that the expression isn't evaluated until the first event is triggered
• Allow .rx.watch() without args to make expression evaluate eagerly
• Update docs

[jbednar]

Thanks. Not sure how we missed some of those earlier. The doc page also needs updating.

[philippjfr]

Thanks. Not sure how we missed some of those earlier. The doc page also needs updating.

I did not fully appreciate that and, or and not cannot be overloaded in Python, only the equivalent boolean operators &, | and ~ can.

[MarcSkovMadsen]

Why are the underscores needed?

[jbednar]

Python keywords cannot be identifiers.

[jbednar]

Looks good to me now, thanks!

[hoxbro]

Is there a way to hook into this updating? An example of this could be adding a loading spinner in Panel if more than 1 second has passed?

[philippjfr]

Quite difficult since most of the time whatever action that is performing the update will be blocking which means you can't simultaneously perform throttling or debouncing on the event.

[hoxbro]

Ok.

[philippjfr]

Looking into it, since now I want this.

[philippjfr]

Will only work for async callbacks and generators though.

[maximlt]

I think the API doc (https://github.com/holoviz/param/blob/main/doc/reference/param/reactive.md) needs to be updated.

[hoxbro]

Other than Maxime suggestion LGTM.