Add a throttled argument to depends, interact and bind

[Hoxbro]

Supersede #1400

The goal of this PR is to discuss the option to add a argument to pn.depends , pn.interact and pn.bind which throttles the slider widgets as mention in #1259.

This is a work in progress and await input from @philippjfr.

For testing purpose I use this script:

from datetime import datetime, date

import panel as pn

pn.extension()

slider_dict = {
    "DateSlider": dict(start=date(2018, 9, 1), end=date(2018, 9, 10)),
    "DateRangeSlider": dict(
        start=date(2018, 9, 1),
        end=date(2018, 9, 10),
        value=(date(2018, 9, 2), date(2018, 9, 4)),
    ),
    "DiscreteSlider": dict(
        options=[0.1, 1, 10, 100],
        value=1,
    ),
    "FloatSlider": dict(start=1, end=10, value=5),
    "IntSlider": dict(start=1, end=10, value=5),
    "IntRangeSlider": dict(start=1, end=10, value=(2, 5)),
    "RangeSlider": dict(start=1, end=10, value=(2, 5)),
}

func = lambda x: repr(x)
throttled = True

dashboard = []
for slider, kwargs in slider_dict.items():
    widget = getattr(pn.widgets, slider)(**kwargs)
    bind = pn.bind(func, widget, throttled=throttled)
    depends = pn.depends(widget, throttled=throttled)(func)
    interact = pn.interact(func, x=widget, throttled=throttled)
    slider = pn.Column("## " + slider, widget, bind, depends, interact)
    dashboard.append(slider)

pn.Row(*dashboard).show()

Missing tasks:

• Discussion if this is the best implementation or the implementation is needed.
• Keyword argument to be used to enable value_throttled on sliders, right now it is throttled.
• Create tests for the chosen implementation.
• Update documentation with the new implementation.
• Other?

[codecov]

Codecov Report

Merging #1754 (36b7c6e) into master (06530a0) will increase coverage by 0.19%.
The diff coverage is 92.68%.

@@            Coverage Diff             @@
##           master    #1754      +/-   ##
==========================================
+ Coverage   84.93%   85.12%   +0.19%     
==========================================
  Files         151      151              
  Lines       17420    17941     +521     
==========================================
+ Hits        14796    15273     +477     
- Misses       2624     2668      +44     

Impacted Files	Coverage Δ
panel/interact.py	74.57% <71.42%> (+0.63%)	⬆️
panel/widgets/slider.py	93.95% <81.81%> (+2.25%)	⬆️
panel/tests/test_interact.py	99.00% <83.33%> (-1.00%)	⬇️
panel/layout/card.py	95.74% <100.00%> (ø)
panel/tests/test_server.py	100.00% <100.00%> (ø)
panel/tests/widgets/test_slider.py	100.00% <100.00%> (ø)
panel/viewable.py	71.54% <0.00%> (-1.77%)	⬇️
panel/pane/holoviews.py	84.04% <0.00%> (-1.03%)	⬇️
panel/command/serve.py	16.84% <0.00%> (-0.55%)	⬇️
panel/compiler.py	11.11% <0.00%> (-0.32%)	⬇️
... and 79 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 556c1f6...36b7c6e. Read the comment docs.

[philippjfr]

I'm a -1 on the changes to bind and depends since you can very easily use widget.param.value_throttled.

[philippjfr]

So what I'd like to see here is removing it from the depends/bind code, adding an example to the interact docs and finally a test.

[philippjfr]

Also happy to see an example showing depends/bind usage with value_throttled, don't have any suggestions on where that should go though.

[Hoxbro]

Thanks for the comments, I will do what you have suggested later this week.

I would just like to mention that I have had a lot of problem finding out the correct way to apply value_throttled argument in depends/interact, when I started learning Panel and I still find myself look at old code to get it to work. I can see I'm properly not the only one which have these problem if I look at the discourse 1416 and 1404, so maybe a documentation page with only documentation and examples of how to use value_throttled could be a good option. This page could then be referenced at each of the slider widgets page.

[MarcSkovMadsen]

@Hoxbro. Why do you use value_throtled at all and what does it do? (I've never used that.)

[xavArtley]

Value throttle is updated only when you end interaction with the widget. For exemple slider send value_throttle only when you release mouse button. It avoid to call too often some functions wich can be time consuming Le ven. 13 nov. 2020 à 11:51, Marc Skov Madsen <notifications@github.com> a écrit :

…

@Hoxbro <https://github.com/Hoxbro>. Why do you use value_throtled at all and what does it do? (I've never used that.) — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#1754 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AENMGS72JDWYBUY6GITHFWLSPUFRPANCNFSM4TPYFYSQ> .

[Hoxbro]

As @xavArtley explained it is for calling a function after the mouse is released from the slider and not continually doing the sliding. When the function takes a long time to calculate it becomes very frustrating because it feels like it takes even longer than it should, see example below. Also if the function has to open a file or look up values from a database it will do it a unnecessary amount of times.

import panel as pn
import time

pn.extension()

def func(x):
    time.sleep(1)
    return repr(x)

widget1 = pn.widgets.IntSlider(start=1, end=100)
widget2 = pn.widgets.IntSlider(start=1, end=100)

slider1 = pn.bind(func, widget1)
slider2 = pn.bind(func, widget2.param.value_throttled)

pn.Column(widget1, slider1, widget2, slider2).servable()

Right now the only options is to add the widget.param.value_throttled as an input instead of just widget. When you have a lot of sliders it becomes more confusing and therefore it would have been nice if there were an option to just use value_throttled instead of value if a widget had it.

Another problem with value_throttled (to my knowledge) is that it is hard to incorporate into a parametrized class, what I do is either what I showed here or just create a "simple" widget.

[philippjfr]

Thanks so much! I'll merge this for now, and further improvements for the docs can come later.

[philippjfr]

The Parameterized class problem is a good point, I think we should allow configuring that in the Param pane widgets argument. Also for a later PR though.