# \#param

**URL:** https://discourse.holoviz.org/tag/param/5.md

[Latest](https://discourse.holoviz.org/latest.md) · [Categories](https://discourse.holoviz.org/categories.md) · [Tags](https://discourse.holoviz.org/tags.md)

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## [Optimizing HoloViews and Param for faster streaming/DynamicMap](https://discourse.holoviz.org/t/optimizing-holoviews-and-param-for-faster-streaming-dynamicmap/9121)

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**Author:** [@SimonHeybrock](https://discourse.holoviz.org/u/SimonHeybrock)\
**Replies:** 6\
**Last updated:** [October 8, 2026, 2:16pm UTC](https://discourse.holoviz.org/t/optimizing-holoviews-and-param-for-faster-streaming-dynamicmap/9121 "2026-10-08T14:16:58Z")

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Optimizing HoloViews and Param for faster streaming/DynamicMap Context We are developing a dashboard using Panel+HoloViews, displaying data streams from Kafka (a variety of 1D and 2D plots). Despite updating only once pe…

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## [How to write into a PointDraw stream?](https://discourse.holoviz.org/t/how-to-write-into-a-pointdraw-stream/5051)

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**Author:** [@szarma](https://discourse.holoviz.org/u/szarma)\
**Replies:** 2\
**Last updated:** [September 7, 2026, 1:41pm UTC](https://discourse.holoviz.org/t/how-to-write-into-a-pointdraw-stream/5051 "2026-09-07T13:41:34Z")

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I need to have sync between a hv.Points plot and a DataFrame, while enabling a PointDraw tool. Yes, this calls for an Annotator, but I don’t know how to extend Annotator with further callbacks. So, I tried the following…

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## [Only executing the dependencies of a tab when active](https://discourse.holoviz.org/t/only-executing-the-dependencies-of-a-tab-when-active/9152)

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**Author:** [@bevilacqc](https://discourse.holoviz.org/u/bevilacqc)\
**Replies:** 2\
**Last updated:** [April 21, 2026, 2:42pm UTC](https://discourse.holoviz.org/t/only-executing-the-dependencies-of-a-tab-when-active/9152 "2026-04-21T14:42:55Z")

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Hello, I have a question which is a follow up of Inactive Tab computes when dynamic=True. I want the code for rendering a tab only be executed when the tab is active, even if there are upstream changes to the parameter…

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## [DynamicMap colorbar ticks will not update when parameter changes](https://discourse.holoviz.org/t/dynamicmap-colorbar-ticks-will-not-update-when-parameter-changes/8591)

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**Author:** [@lee1](https://discourse.holoviz.org/u/lee1)\
**Replies:** 6\
**Last updated:** [January 5, 2026, 5:08pm UTC](https://discourse.holoviz.org/t/dynamicmap-colorbar-ticks-will-not-update-when-parameter-changes/8591 "2026-01-05T17:08:44Z")

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We have a Panel app that has two linked DynamicMaps that have gridded data with point observation data overlayed. The data has 3 different output fields from the model (severity, probability, and SLD) and we have a param…

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## [Panel widgets based on param model not updating when changed in own callback](https://discourse.holoviz.org/t/panel-widgets-based-on-param-model-not-updating-when-changed-in-own-callback/8912)

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**Author:** [@broccoliboy](https://discourse.holoviz.org/u/broccoliboy)\
**Replies:** 2\
**Last updated:** [August 30, 2025, 2:48pm UTC](https://discourse.holoviz.org/t/panel-widgets-based-on-param-model-not-updating-when-changed-in-own-callback/8912 "2025-08-30T14:48:11Z")

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I’m seeing unexpected behavior when trying to update a widget from its own callback on a model built on param.Parameterized. In the following example, using classic panel widgets works as expected. The checkbox resets it…

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## [How to use \`Viewer\` and \`Param\` classes with non-blocking loading pages (long time consuming components)](https://discourse.holoviz.org/t/how-to-use-viewer-and-param-classes-with-non-blocking-loading-pages-long-time-consuming-components/8832)

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**Author:** [@vanheck](https://discourse.holoviz.org/u/vanheck)\
**Replies:** 0\
**Last updated:** [July 3, 2025, 1:42pm UTC](https://discourse.holoviz.org/t/how-to-use-viewer-and-param-classes-with-non-blocking-loading-pages-long-time-consuming-components/8832 "2025-07-03T13:42:14Z")

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Hi, I would like to create a more sophisticated dashboard. However, I’m having trouble combining the param.Parametrized and pn.viewable.Viewer classes with non-blocking loading of data and, effectively, the entire page. …

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## [Why is declarative approach favored over in efficiency imperative approach for interactivity?](https://discourse.holoviz.org/t/why-is-declarative-approach-favored-over-in-efficiency-imperative-approach-for-interactivity/8723)

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**Author:** [@OSuwaidi](https://discourse.holoviz.org/u/OSuwaidi)\
**Replies:** 6\
**Last updated:** [May 28, 2025, 4:35pm UTC](https://discourse.holoviz.org/t/why-is-declarative-approach-favored-over-in-efficiency-imperative-approach-for-interactivity/8723 "2025-05-28T16:35:26Z")

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I am specifically questioning the the example found here where the declarative solution is recommended over the imperative one, but I couldn’t find a clear reason why (it says “declarative approach enhances code maintain…

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## [Problem creating constant parameters with dependencies on mutable parameters](https://discourse.holoviz.org/t/problem-creating-constant-parameters-with-dependencies-on-mutable-parameters/8778)

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**Author:** [@dansawula](https://discourse.holoviz.org/u/dansawula)\
**Replies:** 2\
**Last updated:** [May 28, 2025, 1:04pm UTC](https://discourse.holoviz.org/t/problem-creating-constant-parameters-with-dependencies-on-mutable-parameters/8778 "2025-05-28T13:04:33Z")

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Hi all, New to param/holoviz. When I attempt to create a constant parameter whose value depends on another mutable parameter, there is unexpected behavior when watch=True - the parameter which should be constant is act…

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## [Weird behavior when using template and browser inspect tool](https://discourse.holoviz.org/t/weird-behavior-when-using-template-and-browser-inspect-tool/8720)

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**Author:** [@Davide\_sd](https://discourse.holoviz.org/u/Davide_sd)\
**Replies:** 3\
**Last updated:** [April 30, 2025, 10:51am UTC](https://discourse.holoviz.org/t/weird-behavior-when-using-template-and-browser-inspect-tool/8720 "2025-04-30T10:51:04Z")

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I’m working on a complex application composed of several components. Each component can be a direct instance of param.Parameterized or pn.viewable.Viewer. I’ve been able to create a simple example in order to show this …

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## [How to link two widgets in Panel?](https://discourse.holoviz.org/t/how-to-link-two-widgets-in-panel/8688)

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**Author:** [@Sanders](https://discourse.holoviz.org/u/Sanders)\
**Replies:** 2\
**Last updated:** [April 18, 2025, 11:48am UTC](https://discourse.holoviz.org/t/how-to-link-two-widgets-in-panel/8688 "2025-04-18T11:48:46Z")

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Hi, I’m trying to sync the value of a slider with a dropdown in Panel. Is there a simple way to link them so they update together? Thanks!

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## [Does Param have a concept of unions of types?](https://discourse.holoviz.org/t/does-param-have-a-concept-of-unions-of-types/8685)

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**Author:** [@rosequartz](https://discourse.holoviz.org/u/rosequartz)\
**Replies:** 4\
**Last updated:** [April 16, 2025, 3:51pm UTC](https://discourse.holoviz.org/t/does-param-have-a-concept-of-unions-of-types/8685 "2025-04-16T15:51:37Z")

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Say I’m trying to write a param.ParameterizedFunction subclass that wraps a function f: def f(x: str | int): ... Does param have a way to represent the x parameter that captures that x may either be a str or an int? I …

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## [What triggers component re-rendering (i.e. call \_\_panel\_\_)?](https://discourse.holoviz.org/t/what-triggers-component-re-rendering-i-e-call-panel/8670)

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**Author:** [@jonwetzel](https://discourse.holoviz.org/u/jonwetzel)\
**Replies:** 2\
**Last updated:** [April 2, 2025, 8:58pm UTC](https://discourse.holoviz.org/t/what-triggers-component-re-rendering-i-e-call-panel/8670 "2025-04-02T20:58:42Z")

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I’m making a custom component that manages a list of files the user has selected: import param import panel as pn from panel.viewable import Viewer import logging import os # from src.frontend.components.file\_selector\_m…

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## [I want to know Best Practices for Using Param with HoloViz – I want Suggestions](https://discourse.holoviz.org/t/i-want-to-know-best-practices-for-using-param-with-holoviz-i-want-suggestions/8661)

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**Author:** [@disuja](https://discourse.holoviz.org/u/disuja)\
**Replies:** 1\
**Last updated:** [March 25, 2025, 3:08pm UTC](https://discourse.holoviz.org/t/i-want-to-know-best-practices-for-using-param-with-holoviz-i-want-suggestions/8661 "2025-03-25T15:08:03Z")

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Hey everyone, I have been diving into HoloViz’s Param library & I am impressed with how it simplifies parameterized code when building interactive apps. I feel such as I am just scratching the surface & want advice from…

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## [Pn.widgets.\*.from\_param is very slow to instantiate](https://discourse.holoviz.org/t/pn-widgets-from-param-is-very-slow-to-instantiate/8614)

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**Author:** [@CmpCtrl](https://discourse.holoviz.org/u/CmpCtrl)\
**Replies:** 6\
**Last updated:** [March 16, 2025, 6:55pm UTC](https://discourse.holoviz.org/t/pn-widgets-from-param-is-very-slow-to-instantiate/8614 "2025-03-16T18:55:48Z")

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I was following the doc’s here Create Custom Widget to try to build some custom widgets that i didn’t thing were overly complicated. But, i’m having real issues with performance. I’m trying to build widgets that a user c…

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## [Param State Machine](https://discourse.holoviz.org/t/param-state-machine/8638)

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**Author:** [@ea42gh](https://discourse.holoviz.org/u/ea42gh)\
**Replies:** 0\
**Last updated:** [March 14, 2025, 8:27pm UTC](https://discourse.holoviz.org/t/param-state-machine/8638 "2025-03-14T20:27:01Z")

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There are repeated questions about controlling the execution order of function executions for params. E.g., @param.depends update order and Sequence of events when using Param watchers Is there currently any official w…

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## [ValueError: assignment destination is read-only](https://discourse.holoviz.org/t/valueerror-assignment-destination-is-read-only/4947)

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**Author:** [@StuckDuckF](https://discourse.holoviz.org/u/StuckDuckF)\
**Replies:** 8\
**Last updated:** [March 4, 2025, 2:24pm UTC](https://discourse.holoviz.org/t/valueerror-assignment-destination-is-read-only/4947 "2025-03-04T14:24:59Z")

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I have an app that works the first time but crashes with the included error on second tries. I have isolated it to the hvplot object. I have tried wrapping it, returning from a function and all sorts of workarounds but f…

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## [Runtime Error with Concurrent User Sessions - Models must be owned by only a single document](https://discourse.holoviz.org/t/runtime-error-with-concurrent-user-sessions-models-must-be-owned-by-only-a-single-document/8558)

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**Author:** [@RishikaSatheesh](https://discourse.holoviz.org/u/RishikaSatheesh)\
**Replies:** 6\
**Last updated:** [February 12, 2025, 1:25pm UTC](https://discourse.holoviz.org/t/runtime-error-with-concurrent-user-sessions-models-must-be-owned-by-only-a-single-document/8558 "2025-02-12T13:25:44Z")

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Hi, I’m deploying an application that uses Param and Panel to create an interactive visualization tool. However, I’m encountering the following error when multiple users open sessions concurrently and click the Submit bu…

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## [How to remove sync parameters from the URL linked to the title when using Template?](https://discourse.holoviz.org/t/how-to-remove-sync-parameters-from-the-url-linked-to-the-title-when-using-template/8554)

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**Author:** [@monodera](https://discourse.holoviz.org/u/monodera)\
**Replies:** 0\
**Last updated:** [February 3, 2025, 7:19pm UTC](https://discourse.holoviz.org/t/how-to-remove-sync-parameters-from-the-url-linked-to-the-title-when-using-template/8554 "2025-02-03T19:19:44Z")

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When I use pn.state.location.sync with a Template, the URL linked to the title includes the synced parameters. Is it possible to remove them from the URL? In the following example, I’d like to have a link as http://loca…

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## [FloatPanel and contained bug ?](https://discourse.holoviz.org/t/floatpanel-and-contained-bug/8513)

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**Author:** [@Serker](https://discourse.holoviz.org/u/Serker)\
**Replies:** 0\
**Last updated:** [January 14, 2025, 3:59pm UTC](https://discourse.holoviz.org/t/floatpanel-and-contained-bug/8513 "2025-01-14T15:59:18Z")

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Hi, I’ve just recently started using Panel and I’m having a problem with FloatPanel Behavior. The MWE is the following: import panel as pn import param from panel.widgets.base import WidgetBase from panel.custom impor…

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## [Rx Marks the Spot: A Prescription for Reactive Python](https://discourse.holoviz.org/t/rx-marks-the-spot-a-prescription-for-reactive-python/8510)

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**Author:** [@ahuang11](https://discourse.holoviz.org/u/ahuang11)\
**Replies:** 0\
**Last updated:** [January 11, 2025, 12:17am UTC](https://discourse.holoviz.org/t/rx-marks-the-spot-a-prescription-for-reactive-python/8510 "2025-01-11T00:17:22Z")

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In this blog post, I’ll walkthrough: how to use rx converting pn.bind into rx expressions example use cases And along the way, highlight pitfalls when using rx. TLDR: A lambda is to a Python function as rx is to…

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## [How to set the text in an SVG image as text instead of paths when saving the SVG, so that it can be edited in Adobe Illustrator?](https://discourse.holoviz.org/t/how-to-set-the-text-in-an-svg-image-as-text-instead-of-paths-when-saving-the-svg-so-that-it-can-be-edited-in-adobe-illustrator/8501)

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**Author:** [@z626093820](https://discourse.holoviz.org/u/z626093820)\
**Replies:** 4\
**Last updated:** [January 9, 2025, 6:35am UTC](https://discourse.holoviz.org/t/how-to-set-the-text-in-an-svg-image-as-text-instead-of-paths-when-saving-the-svg-so-that-it-can-be-edited-in-adobe-illustrator/8501 "2025-01-09T06:35:08Z")

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How to set the text in an SVG image as text instead of paths when saving the SVG, so that it can be edited in Adobe Illustrator?

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## [Helpful best practices when dashboards with param and panel](https://discourse.holoviz.org/t/helpful-best-practices-when-dashboards-with-param-and-panel/8503)

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**Author:** [@kdheepak](https://discourse.holoviz.org/u/kdheepak)\
**Replies:** 0\
**Last updated:** [January 7, 2025, 8:58pm UTC](https://discourse.holoviz.org/t/helpful-best-practices-when-dashboards-with-param-and-panel/8503 "2025-01-07T20:58:15Z")

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Hi all, I really liked this post from /u/ahuang11: I think it’s a great idea to post learnings from making complicated applications. I recently also finished making my first real world app using param and panel at wo…

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## [Changes to a param.rx variable do not trigger UI redraws and don't notify watchers consistently](https://discourse.holoviz.org/t/changes-to-a-param-rx-variable-do-not-trigger-ui-redraws-and-dont-notify-watchers-consistently/8475)

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**Author:** [@Lennart-Rein](https://discourse.holoviz.org/u/Lennart-Rein)\
**Replies:** 3\
**Last updated:** [December 20, 2024, 1:48pm UTC](https://discourse.holoviz.org/t/changes-to-a-param-rx-variable-do-not-trigger-ui-redraws-and-dont-notify-watchers-consistently/8475 "2024-12-20T13:48:33Z")

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Hey everyone, below you will find a minimum example that reproduces the troubles I have been having. In the example I have a Widget with a Button that adds a new entry to a reactive list for every click. The length of …

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## [Sparse Key Dimensions](https://discourse.holoviz.org/t/sparse-key-dimensions/8441)

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**Author:** [@ehsansaleh](https://discourse.holoviz.org/u/ehsansaleh)\
**Replies:** 1\
**Last updated:** [December 3, 2024, 8:59pm UTC](https://discourse.holoviz.org/t/sparse-key-dimensions/8441 "2024-12-03T20:59:53Z")

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Hi there, I was looking at the following example from the documentation on DynamicMap : # credit: https://holoviews.org/user\_guide/Dashboards.html def load\_symbol(symbol, variable, \*\*kwargs): df = pd.DataFrame(get…

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## [Throttling, \`pn.bind\` and using button to reset values](https://discourse.holoviz.org/t/throttling-pn-bind-and-using-button-to-reset-values/8341)

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**Author:** [@jnareb](https://discourse.holoviz.org/u/jnareb)\
**Replies:** 6\
**Last updated:** [November 11, 2024, 2:24pm UTC](https://discourse.holoviz.org/t/throttling-pn-bind-and-using-button-to-reset-values/8341 "2024-11-11T14:24:27Z")

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I want to have some sliders, and a button that resets them to default values. Currently the code looks like this: xrange\_slider = pn.widgets.RangeSlider( name='X Range Slider', start=-10, end=+10, value=(-3, +3), st…

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## [Using query parameters without param](https://discourse.holoviz.org/t/using-query-parameters-without-param/8380)

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**Author:** [@MP-MaximilianLattka](https://discourse.holoviz.org/u/MP-MaximilianLattka)\
**Replies:** 1\
**Last updated:** [November 4, 2024, 5:06pm UTC](https://discourse.holoviz.org/t/using-query-parameters-without-param/8380 "2024-11-04T17:06:21Z")

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Hey there, I’m curious whether it is possible to use query parameters (see Access and Manipulate the URL with pre-existing code featuring “regular” panel widgets. E.g., I’m using the TextInput widget and want to link i…

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## [Easiest way to trigger all watchers of an rx function](https://discourse.holoviz.org/t/easiest-way-to-trigger-all-watchers-of-an-rx-function/8374)

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**Author:** [@edart](https://discourse.holoviz.org/u/edart)\
**Replies:** 0\
**Last updated:** [October 30, 2024, 12:52am UTC](https://discourse.holoviz.org/t/easiest-way-to-trigger-all-watchers-of-an-rx-function/8374 "2024-10-30T00:52:34Z")

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Hi, If I have a function that takes no arguments, but still needs to feed into an rx network as an input, what’s the best way to “tick” that function to all its watchers? Or send them all an event where old=new=rx.value…

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## [Does sphinx autodoc work with param?](https://discourse.holoviz.org/t/does-sphinx-autodoc-work-with-param/1600)

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**Author:** [@ahuang11](https://discourse.holoviz.org/u/ahuang11)\
**Replies:** 8\
**Last updated:** [October 25, 2024, 5:52am UTC](https://discourse.holoviz.org/t/does-sphinx-autodoc-work-with-param/1600 "2024-10-25T05:52:48Z")

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If I made a parameterized class, does it work with sphinx’s autodoc?

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## [How to group settings within a panel](https://discourse.holoviz.org/t/how-to-group-settings-within-a-panel/8292)

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**Author:** [@richardwhitehead](https://discourse.holoviz.org/u/richardwhitehead)\
**Replies:** 14\
**Last updated:** [October 18, 2024, 3:34pm UTC](https://discourse.holoviz.org/t/how-to-group-settings-within-a-panel/8292 "2024-10-18T15:34:04Z")

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I have built a complex control system for a scientific instrument. Settings are implemented as Param objects, with one Parameterized class for each component of the instrument. Settings are displayed in a UI using Panel,…

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## [How to create nested panel?](https://discourse.holoviz.org/t/how-to-create-nested-panel/8310)

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**Author:** [@nknavasto](https://discourse.holoviz.org/u/nknavasto)\
**Replies:** 3\
**Last updated:** [October 5, 2024, 9:35am UTC](https://discourse.holoviz.org/t/how-to-create-nested-panel/8310 "2024-10-05T09:35:34Z")

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I am investigating on how to use panel with param on nested parameters and how to properly display the parameters. Consider the minimum working example below: import panel as pn import param pn.extension() class Pe…

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