Add Widget.from_param classmethod

[philippjfr]

Simplifies the creation of a widget linked to and created from a particular parameter.

import param

class A(param.Parameterized):
    
    value = param.Number()
    
a = A()

pn.widgets.FloatSlider.from_param(a.param.value, start=0, end=3.14)

@maximlt @MarcSkovMadsen Any thoughts on this? It's a solution to something I think you both brought up before. If you like the idea maybe we should also consider a shorter method name than from_parameter, suggestions welcome.

[codecov]

Codecov Report

Merging #1344 into master will increase coverage by 0.19%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master    #1344      +/-   ##
==========================================
+ Coverage   87.49%   87.69%   +0.19%     
==========================================
  Files         130      130              
  Lines       13758    13976     +218     
==========================================
+ Hits        12038    12256     +218     
  Misses       1720     1720              

Impacted Files	Coverage Δ
panel/widgets/base.py	85.22% <33.33%> (-1.84%)	⬇️
panel/tests/test_param.py	99.88% <0.00%> (+0.02%)	⬆️
panel/param.py	92.77% <0.00%> (+1.32%)	⬆️

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[jbednar]

If you like the idea maybe we should also consider a shorter method name than from_parameter, suggestions welcome.

I got as far as the title on this page before my brain went (a) nice! and (b) can we have a shorter name? :-) How about just from, currently supporting Parameters but e.g. supporting a traitlet or some other source potentially? You could maybe also consider it another type of linking, and make .link() be either an instance or class method, where it does this when called on the class.

[maximlt]

I don't remember if I ever brought this up but I'll still give you my 2 cents!

This

pn.widgets.FloatSlider.from_parameter(a.param.value, start=0, end=3.14)

is better than

pn.Param(a.param.value, widgets={"value": {"type": pn.widgets.FloatSlider, "start":0, "end":3.14}})

That's even better :-)

pn.widgets.FloatSlider.from(a.param.value, start=0, end=3.14)

As for the implementation, is it intended that it returns a Param pane and not a widget? I guess I'd expect a widget. It'd make it clearer that this method is intended to create a single widget linked to a parameter and that it would not overlap (too much) with what can already be achieved with the Param pane. It can indeed be finely customized if one sets the precedence of the parameters and/or uses the keyword args parameters and/or widgets. I have sometimes the feeling that there are too many ways to achieve the same thing in panel, just trying to avoid that.

[philippjfr]

As for the implementation, is it intended that it returns a Param pane and not a widget?

No, I think it should return the widget as you point out.

[philippjfr]

Oh and .from won't work since it's a reserved name in Python, any other suggestions?

[maximlt]

Arf missed that. I like that the method starts with from, I'm sometimes confused with .link (that I don't use much TBH), by mistake I could write a.param.value.link(pn.widgets.FloatSlider, start=0, end=3.14)...
Explicit is better than implicit, from_param ? (+ from_trait later on?)

[philippjfr]

Yeah, I'm also leaning towards .from_param, not a huge fan of overly generic methods.