Features

This package provides a new API for creating Dash layout and callbacks.

• The id and children are managed automatically. No deeply nested dicts and lists any more; unique ids of components are automatically created.

• A re-usable template can be defined by sub-classing dash_component_template.ComponentTemplate. Instances of the template have children with unique ids and can be used anywhere in anyway inside a larger Dash app layout tree.

Get Started

Suppose we have the following Dash app (from Dash tutorial site):

# Run this app with `python app.py` and
# visit http://127.0.0.1:8050/ in your web browser.

import dash
from dash import dcc, html
import plotly.express as px
import pandas as pd

app = dash.Dash(__name__)

# assume you have a "long-form" data frame
# see https://plotly.com/python/px-arguments/ for more options
df = pd.DataFrame({
    "Fruit": ["Apples", "Oranges", "Bananas", "Apples", "Oranges", "Bananas"],
    "Amount": [4, 1, 2, 2, 4, 5],
    "City": ["SF", "SF", "SF", "Montreal", "Montreal", "Montreal"]
})

fig = px.bar(df, x="Fruit", y="Amount", color="City", barmode="group")

app.layout = html.Div(children=[
    html.H1(children='Hello Dash'),

    html.Div(children='''
        Dash: A web application framework for your data.
    '''),

    dcc.Graph(
        id='example-graph',
        figure=fig
    )
])

if __name__ == '__main__':
    app.run_server(debug=True)

Let’s build a new app which have two columns of the same layout.

from dash_component_template import ComponentTemplate
import dash_bootstrap_components as dbc
import pandas as pd
import dash
import plotly.express as px
from dash import html, dcc


# This class defines a template that resembles the Dash example,
# with a title, subtitle, and graph for visualizing a data frame
class MyTableGraph(ComponentTemplate):

    class Meta:
        component_cls = dbc.Container

    def __init__(self, title_text, subtitle_text, df, parent=None):
        super().__init__(parent=parent)
        self._title_text = title_text
        self._subtitle_text = subtitle_text
        self._df = df

    def setup_layout(self, app):
        container = self
        container.child(html.Div, self._title_text)
        container.child(html.Div, self._subtitle_text)
        container.child(dcc.Graph, figure=self._make_fig())
        super().setup_layout(app)

    def _make_fig(self):
        return px.bar(
            self._df, x="Fruit", y="Amount", color="City", barmode="group")


# This class defines the app layout which have two columns each column
# contains an instance of the template defined above.

class MyPage(ComponentTemplate):

    class Meta:
        component_cls = dbc.Container

    # define some data
    df1 = pd.DataFrame({
        "Fruit": [
            "Apples", "Oranges", "Bananas", "Apples", "Oranges", "Bananas"],
        "Amount": [4, 1, 2, 2, 4, 5],
        "City": ["SF", "SF", "SF", "Montreal", "Montreal", "Montreal"]
    })

    df2 = pd.DataFrame({
        "Fruit": [
            "Apples", "Oranges", "Bananas", "Apples", "Oranges", "Bananas"],
        "Amount": [5, 6, 7, 8, 4, 5],
        "City": ["SF", "SF", "SF", "Montreal", "Montreal", "Montreal"]
    })

    def setup_layout(self, app):
        col1, col2 = self.grid(nrows=1, ncols=2, squeeze=True)
        col1.child(MyTableGraph(
            df=self.df1,
            title_text='Hello Dash (left)',
            subtitle_text='Re-usable template instance 1'
            ))
        col2.child(MyTableGraph(
            df=self.df2,
            title_text='Hello Dash (right)',
            subtitle_text='Re-usable template instance 2'
            ))
        # this line is important which triggers children's setup_layout
        super().setup_layout(app)


# Now create the app and set the bootstrap css
app = dash.Dash(__name__, external_stylesheets=[dbc.themes.BOOTSTRAP])

# Instantiant the page tempalte, and call the setup layout function
# This only "declare" the structure of the Dash components. No actual
# Dash components are created yet.
page = MyPage()
page.setup_layout(app)
# Create and assign the app layout. The actual creation of Dash components
# are done here.
app.layout = page.layout

if __name__ == '__main__':
    app.run_server(debug=True)

Live Examples

Live examples can be found in the TolTEC DR site.

Credits

This package was created with Cookiecutter and the audreyr/cookiecutter-pypackage project template.

0.1.0 (2021-11-09)

• First release on PyPI.