Panel Material UI Development Skills

This guide provides best practices for using Panel Material UI. Optimized for LLMs.

Please develop code, tests and documentation as an expert Panel analytics app developer would do when working with a short time to market.

If not already loaded please get the ‘panel’ skill.

This guide focuses on panel-material-ui specific patterns. This guide takes precedence over the panel skills.

Installation

pip install panel-material-ui panel watchfiles hvplot hvsampledata

For development in .py files DO always include watchfiles for hotreload.

Best Practice Hello World App

Let’s describe our best practices via a basic Hello World App:

# DO import panel as pn
import panel as pn
# DO import panel_material_ui as pmui
import panel_material_ui as pmui
import param

# DO run pn.extension
# DO remember to add any imports needed by panes, e.g. pn.extension("tabulator", "plotly", ...)
# DON'T add "bokeh" as an extension. It is not needed.
# DON'T add "panel_material_ui" as an extension. It is not needed.
# Do use throttled=True when using slider unless you have a specific reason not to
pn.extension(throttled=True)

# DO organize functions to extract data separately as your app grows
# DO use caching to speed up the app, e.g. for expensive data loading or processing that would return the same result given same input arguments.
# DO add a ttl (time to live argument) for expensive data loading that changes over time
@pn.cache(max_items=3)
def extract(n=5):
    return "Hello World" + "⭐" * n

text = extract()
text_len = len(text)

# DO organize functions to transform data separately as your app grows. Eventually in a separate transform.py file
# DO add caching to speed up expensive data transformations
def transform(data: str, count: int=5)->str:
    """
    Transforms the input data by truncating it to the specified count of characters.
    """
    count = min(count, len(data))
    return data[:count]

# DO organize functions to create plots separately as your app grows. Eventually in a separate plots.py file.
# DO organize custom components and views separately as your app grows. Eventually in separate components.py or views.py file(s).

# DO use param.Parameterized, pn.viewable.Viewer or similar approach to create new components and apps with state and reactivity
class HelloWorld(pn.viewable.Viewer):
    """
    A simple Panel app that displays a "Hello World" message with a slider to control the length of the message.
    """
    # DO define parameters to hold state and drive the reactivity
    characters = param.Integer(default=text_len, bounds=(0, text_len), doc="Number of characters to display")

    def __init__(self, **params):
        super().__init__(**params)

        # DO use sizing_mode="stretch_width" for components unless "fixed" or other sizing_mode is specifically needed
        with pn.config.set(sizing_mode="stretch_width"):
            # DO create widgets using `.from_param` method
            self._characters_input = pmui.IntSlider.from_param(self.param.characters, margin=(10,20))
             # DO Collect input widgets into horizontal, columnar layout unless other layout is specifically needed
            self._inputs = pmui.Column(self._characters_input, max_width=300)
             # DO collect output components into some layout like Column, Row, FlexBox or Grid depending on use case
            self._outputs = pmui.Column(self.model)
            self._panel = pmui.Row(self._inputs, self._outputs)


    # DO use caching to speed up bound methods that are expensive to compute or load data and return the same result for a given state of the class.
    @pn.cache
    # DO prefer .depends over .bind over .rx for reactivity methods on Parameterized classes as it can be typed and documented
    # DON'T use `watch=True` or `.watch` methods to update UI. Only for updating overall app or component state.
    # DO use `watch=True` or `.watch` for triggering side effect like saving file or sending email.
    @param.depends("characters")
    def model(self):
        """
        Returns the "Hello World" message truncated to the specified number of characters.
        """
        return transform(text, self.characters)

    # DO provide a method for displaying the component in a notebook setting, i.e. without using a Template or Page element
    def __panel__(self):
        return self._panel

    # DO provide a method to create a .servable app
    @classmethod
    def create_app(cls, **params):
        """
        Create the Panel app with the interactive model and slider.
        """
        instance = cls(**params)
        # DO use the `Page` to layout the served app unless otherwise specified
        return pmui.Page(
            # DO provide a title for the app
            title="Hello World App",
            # DO provide optional image, optional app description, optional navigation menu, input widgets, optional documentation and optional links in the sidebar
            # DO provide as list of components or a list of single horizontal layout like Column as the sidebar by default is 300 px wide
            sidebar=list(instance._inputs),
            # DO provide a list of layouts and output components in the main area of the app.
            # DO use Grid or FlexBox layouts for complex dashboard layouts instead of combination Rows and Columns.
            main=list(instance._outputs),
        )

# DO provide a method for quick development preview with `python`
if __name__ == "__main__":
    # DO run with `python path_to_this_file.py` for quick development preview
    HelloWorld.create_app().show(port=5007, autoreload=True, open=True)
# DO provide a method to serve the app with `panel serve`
elif pn.state.served:
    # DO run with `panel serve path_to_this_file.py --port 5007 --dev` add `--show` to open the app in a browser
    HelloWorld.create_app().servable() # DO mark the element(s) to serve with .servable()

DO always create test in separate test files and DO run test via pytest:

import ...

# DO put tests into separate test file(s)
# DO test the reactivity of each parameter, function, method, component or app.
# DO run pytest when the code is changed. DON'T create non-pytest scripts or files to test the code.
def test_characters_reactivity():
    """
    Always test that the reactivity works as expected.
    Put tests in a separate test file.
    """
    # Test to be added in separate test file
    hello_world = HelloWorld()
    assert hello_world.model() == text[:hello_world.characters] # DO test the default values of bound methods
    hello_world.characters = 5
    assert hello_world.model() == text[:5] # DO test the reactivity of bound methods when parameters change
    hello_world.characters = 3
    assert hello_world.model() == text[:3]

Panel Material UI Guidelines

General Instructions

• DO use the new parameter names (e.g. label, color) instead of legacy aliases (e.g. name, button_type) for pmui components
• DO use sizing_mode parameter over sx css styling parameter
• DO use Material UI sx parameter for all css styling over styles and stylesheets
• DO use panel-material-ui components instead of panel components for projects already using panel-material-ui and for new projects
• DON’T configure the design, i.e. DO NOT pn.extension(design='material').
• DO prefer professional Material UI icons over emojies

Component Instructions

Page

• DO provide the title to the Page.title argument. DON’T provide it in the Page.main area.
• DO make sure components in the sidebar stretch width.
• DO provide an optional image, description, navigation menu to the Page.sidebar argument. Normally DON’t put them in the header or main areas.
• DO provide the input widgets as children to the Page.sidebar argument
• DO not add advanced or high components to the Page.header as it is only 100px high by default. Normally only buttons, indicators, text and navigation links go into the header.
• DON’T include ThemeToggle or other widgets to toggle the theme when using the Page. A ThemeToggle is already built in.
• DO Add a little bit of margin=10 to the outer layout component(s) in the main area. To make them stand out from the sidebar components: Grid(..., container=True, margin=15).

DO provide lists of children to the Page.sidebar, Page.main or Page.header arguments:

pmui.Page(
    header=[component1, component2],  # This is correct
    sidebar=[component3, component4],  # This is correct
    main=[a_list_like_layout, a_grid],  # This is correct
)

DON’T provide non-lists as children to the Page.sidebar, Page.main or Page.header arguments:

pmui.Page(
    header=component1,  # This is incorrect
    sidebar=list(a_list_like_layout),  # This is incorrect
    main=list(a_grid),  # This is incorrect
)

Linking Dashboard Theme with Page Theme

DO synchronize component themes with Page theme:

    ...

    dark_theme = param.Boolean(
        doc="""True if the theme is dark""",
        # To enable providing parameters and bound function references
        allow_refs=True
        )

    @classmethod
    def create_app(cls, **params):
        """Create app with synchronized theming."""
        component = cls(**params)

        page = pmui.Page(
            ...,
            dark_theme=component.dark_theme,  # Pass theme to Page
        )

        # Synchronize Page theme to component theme
        component.dark_theme = page.param.dark_theme
        return page

Grid

• DO set spacing=2 or higher to separate sub components in the grid.
• DO not use ncols keyword argument. It is not supported.

Column/ Row

• DO use size parameter instead of xs, sm or md parameters – they do not exist.
• DO use sx to set spacing instead of setting spacing directly. It does not exist.

List like layouts

For list-like layouts like Column and Row DO provide children as positional arguments:

pmui.Row(child1, child2, child3) # DO

DON’T provide them as separate arguments:

pmui.Row([child1, child2, child3,]) # DON'T

Paper

DO change the default margin to 10px:

pmui.Paper.param.margin.default=10

Switch

• Do add margin=(10, 20) when displaying in the sidebar.

Sliders

• DO add a little bit of margin left and right when displaying in the sidebar.

Cards

• DO use the Paper component over the Card unless you need the Cards extra features.
• DO set collapsible=False unless collapsible is needed.

Tabulator

• DO use “materialize” theme instead of “material”. The latter does not exist.

Non-Existing Components

• Do use Column instead of Box. The Box component does not exist.

Material UI Examples

Standalone Icons

DO use Typography to make standalone icons without interactivity instead of IconButton:

# CORRECT: Typography for standalone decorative icons
pmui.Typography(
    f'<span class="material-icons" style="font-size: 4rem;">lightbulb</span>',
    sizing_mode="fixed", width=60, height=60, sx = {"color": "primary.main"},
)
# INCORRECT: IconButton for decorative icons
pmui.IconButton(icon=icon, disabled=True, ...)

Static Components Pattern (Material UI)

import panel as pn
import panel_material_ui as pmui
import param

pn.extension()

pmui.Paper.param.margin.default=10

class HelloWorld(pn.viewable.Viewer):
    characters = param.Integer(default=10, bounds=(1, 100), doc="Number of characters to display")

    def _get_kpi_card(self):
        # Create a static layout once
        return pmui.Paper(
            pmui.Column(
                pmui.Typography(
                    "📊 Key Performance Metrics",
                    variant="h6",
                    sx={
                        "color": "text.primary",
                        "fontWeight": 700,
                        "mb": 3,
                        "display": "flex",
                        "alignItems": "center",
                        "gap": 1
                    }
                ),
                pmui.Row(
                    # Use a reactive/ bound/ reference value for dynamic content
                    self.kpi_value
                )
            ),
        )

    @param.depends("characters")
    def kpi_value(self):
        return f"The kpi is {self.characters}"

    def __panel__(self):
        return pmui.Paper(
            pmui.Column(
                self.param.characters,
                self._get_kpi_card(),
            ),
            sx={"padding": "20px", "borderRadius": "8px"},
            sizing_mode="stretch_width"
        )

if pn.state.served:
    HelloWorld().servable()

For all other Panel patterns (parameter-driven architecture, reactive updates, serving, etc.), refer tot the ‘panel’ skill.