Dash

"""
Minimal Example
===============
Generating a square wordcloud from the US constitution using default arguments.
"""

import os

from os import path
from wordcloud import WordCloud

# get data directory (using getcwd() is needed to support running example in generated IPython notebook)
d = path.dirname(__file__) if "__file__" in locals() else os.getcwd()

# Read the whole text.
text = open(path.join(d, 'constitution.txt')).read()

# Generate a word cloud image
wordcloud = WordCloud().generate(text)

# Display the generated image:
# the matplotlib way:
import matplotlib.pyplot as plt
plt.imshow(wordcloud, interpolation='bilinear')
plt.axis("off")

# lower max_font_size
wordcloud = WordCloud(max_font_size=40).generate(text)
plt.figure()
plt.imshow(wordcloud, interpolation="bilinear")
plt.axis("off")
plt.show()

# The pil way (if you don't have matplotlib)
# image = wordcloud.to_image()
# image.show()

https://plot.ly/dash/

https://dash.plot.ly/

Material from the Udemy's course I'm doing: https://www.udemy.com/course/interactive-python-dashboards-with-plotly-and-dash/

Dash apps consist of a Flask server that communicates with front-end React components using JSON packets over HTTP requests. https://www.tutorialspoint.com/python_web_development_libraries/python_web_development_libraries_dash_framework.htm

Installation

https://dash.plot.ly/installation

pip install dash==1.7.0

# Note: starting with dash 0.37.0, dash automatically installs dash-renderer, dash-core-components, dash-html-components, and dash-table, using known-compatible versions of each. You need not and should not install these separately any longer, only dash itself.

A quick note on checking your versions and on upgrading. These docs are run using the versions listed above and these versions should be the latest versions available. To check which version that you have installed, you can run e.g:

>>> import dash_core_components
>>> print(dash_core_components.__version__)

To see the latest changes of any package, check the GitHub repo's CHANGELOG.md file:

dash & dash-renderer changelog
- dash-renderer is a separate package installed automatically with dash but its updates are included in the main dash changelog. These docs are using dash-renderer==1.1.2.
dash-core-components changelog
dash-html-components changelog
dash-table changelog
plotly changelog
- the plotly package is also installed automatically with dash. It is the Python interface to the plotly.js graphing library, so is mainly used by dash-core-components, but it's also used by dash itself. These docs are using plotly==3.3.0.

All of these packages adhere to semver.

Examples

Dash App Gallery: https://dash-gallery.plotly.host/Portal/

This one is with a sidebar: https://dash-gallery.plotly.host/dash-svm/
https://dash-gallery.plotly.host/dash-oil-and-gas/
https://dash-gallery.plotly.host/dash-web-trader/

Dash Core Components Gallery: https://dash.plot.ly/dash-core-components

Example 2

app.py

import dash
import dash_core_components as dcc
import dash_html_components as html
import pandas as pd
import plotly.graph_objs as go

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash(__name__, external_stylesheets=external_stylesheets)

df = pd.read_csv(
    'https://gist.githubusercontent.com/chriddyp/'
    'cb5392c35661370d95f300086accea51/raw/'
    '8e0768211f6b747c0db42a9ce9a0937dafcbd8b2/'
    'indicators.csv')

available_indicators = df['Indicator Name'].unique()

app.layout = html.Div([
    html.Div([

        html.Div([
            dcc.Dropdown(
                id='crossfilter-xaxis-column',
                options=[{'label': i, 'value': i} for i in available_indicators],
                value='Fertility rate, total (births per woman)'
            ),
            dcc.RadioItems(
                id='crossfilter-xaxis-type',
                options=[{'label': i, 'value': i} for i in ['Linear', 'Log']],
                value='Linear',
                labelStyle={'display': 'inline-block'}
            )
        ],
        style={'width': '49%', 'display': 'inline-block'}),

        html.Div([
            dcc.Dropdown(
                id='crossfilter-yaxis-column',
                options=[{'label': i, 'value': i} for i in available_indicators],
                value='Life expectancy at birth, total (years)'
            ),
            dcc.RadioItems(
                id='crossfilter-yaxis-type',
                options=[{'label': i, 'value': i} for i in ['Linear', 'Log']],
                value='Linear',
                labelStyle={'display': 'inline-block'}
            )
        ], style={'width': '49%', 'float': 'right', 'display': 'inline-block'})
    ], style={
        'borderBottom': 'thin lightgrey solid',
        'backgroundColor': 'rgb(250, 250, 250)',
        'padding': '10px 5px'
    }),

    html.Div([
        dcc.Graph(
            id='crossfilter-indicator-scatter',
            hoverData={'points': [{'customdata': 'Japan'}]}
        )
    ], style={'width': '49%', 'display': 'inline-block', 'padding': '0 20'}),
    html.Div([
        dcc.Graph(id='x-time-series'),
        dcc.Graph(id='y-time-series'),
    ], style={'display': 'inline-block', 'width': '49%'}),

    html.Div(dcc.Slider(
        id='crossfilter-year--slider',
        min=df['Year'].min(),
        max=df['Year'].max(),
        value=df['Year'].max(),
        marks={str(year): str(year) for year in df['Year'].unique()}
    ), style={'width': '49%', 'padding': '0px 20px 20px 20px'})
])


@app.callback(
    dash.dependencies.Output('crossfilter-indicator-scatter', 'figure'),
    [dash.dependencies.Input('crossfilter-xaxis-column', 'value'),
     dash.dependencies.Input('crossfilter-yaxis-column', 'value'),
     dash.dependencies.Input('crossfilter-xaxis-type', 'value'),
     dash.dependencies.Input('crossfilter-yaxis-type', 'value'),
     dash.dependencies.Input('crossfilter-year--slider', 'value')])
def update_graph(xaxis_column_name, yaxis_column_name,
                 xaxis_type, yaxis_type,
                 year_value):
    dff = df[df['Year'] == year_value]

    return {
        'data': [go.Scatter(
            x=dff[dff['Indicator Name'] == xaxis_column_name]['Value'],
            y=dff[dff['Indicator Name'] == yaxis_column_name]['Value'],
            text=dff[dff['Indicator Name'] == yaxis_column_name]['Country Name'],
            customdata=dff[dff['Indicator Name'] == yaxis_column_name]['Country Name'],
            mode='markers',
            marker={
                'size': 15,
                'opacity': 0.5,
                'line': {'width': 0.5, 'color': 'white'}
            }
        )],
        'layout': go.Layout(
            xaxis={
                'title': xaxis_column_name,
                'type': 'linear' if xaxis_type == 'Linear' else 'log'
            },
            yaxis={
                'title': yaxis_column_name,
                'type': 'linear' if yaxis_type == 'Linear' else 'log'
            },
            margin={'l': 40, 'b': 30, 't': 10, 'r': 0},
            height=450,
            hovermode='closest'
        )
    }


def create_time_series(dff, axis_type, title):
    return {
        'data': [go.Scatter(
            x=dff['Year'],
            y=dff['Value'],
            mode='lines+markers'
        )],
        'layout': {
            'height': 225,
            'margin': {'l': 20, 'b': 30, 'r': 10, 't': 10},
            'annotations': [{
                'x': 0, 'y': 0.85, 'xanchor': 'left', 'yanchor': 'bottom',
                'xref': 'paper', 'yref': 'paper', 'showarrow': False,
                'align': 'left', 'bgcolor': 'rgba(255, 255, 255, 0.5)',
                'text': title
            }],
            'yaxis': {'type': 'linear' if axis_type == 'Linear' else 'log'},
            'xaxis': {'showgrid': False}
        }
    }


@app.callback(
    dash.dependencies.Output('x-time-series', 'figure'),
    [dash.dependencies.Input('crossfilter-indicator-scatter', 'hoverData'),
     dash.dependencies.Input('crossfilter-xaxis-column', 'value'),
     dash.dependencies.Input('crossfilter-xaxis-type', 'value')])
def update_y_timeseries(hoverData, xaxis_column_name, axis_type):
    country_name = hoverData['points'][0]['customdata']
    dff = df[df['Country Name'] == country_name]
    dff = dff[dff['Indicator Name'] == xaxis_column_name]
    title = '<b>{}</b><br>{}'.format(country_name, xaxis_column_name)
    return create_time_series(dff, axis_type, title)


@app.callback(
    dash.dependencies.Output('y-time-series', 'figure'),
    [dash.dependencies.Input('crossfilter-indicator-scatter', 'hoverData'),
     dash.dependencies.Input('crossfilter-yaxis-column', 'value'),
     dash.dependencies.Input('crossfilter-yaxis-type', 'value')])
def update_x_timeseries(hoverData, yaxis_column_name, axis_type):
    dff = df[df['Country Name'] == hoverData['points'][0]['customdata']]
    dff = dff[dff['Indicator Name'] == yaxis_column_name]
    return create_time_series(dff, axis_type, yaxis_column_name)


if __name__ == '__main__':
    app.run_server(debug=True, port=8051)

To run the app:

python app.py

Deploying Dash Apps

https://dash.plot.ly/deployment

Dash uses Flask under the hood. This makes deployment easy: you can deploy a Dash app just like you would deploy a Flask app. Almost every cloud server provider has a guide for deploying Flask apps. There is also a Dash Deployment Server, but is not free (commercial).

Flask Deployment
Dash Deployment Server (commercial)

Flask Deployment

https://flask.palletsprojects.com/en/1.1.x/deploying/

Gunicorn

https://flask.palletsprojects.com/en/1.1.x/deploying/wsgi-standalone/#gunicorn

https://gunicorn.org/

Installation:
https://anaconda.org/conda-forge/gunicorn
conda install -c conda-forge gunicorn
or
pip install gunicorn

Gunicorn «Green Unicorn» is a WSGI HTTP Server for UNIX. It's a pre-fork worker model ported from Ruby's Unicorn project. It supports both eventlet and greenlet. Running a Flask application on this server is quite simple:

gunicorn myproject:app

Gunicorn provides many command-line options (see gunicorn -h). For example, to run a Flask application with 4 worker processes (-w 4) binding to localhost port 4000 (-b 127.0.0.1:4000):

gunicorn -w 4 -b 127.0.0.1:4000 myproject:app

The gunicorn command expects the names of your application module or package and the application instance within the module. If you use the application factory pattern, you can pass a call to that:

gunicorn "myproject:create_app()"

First example:

def app(environ, start_response):
        data = b"Hello, World!\n"
        start_response("200 OK", [
            ("Content-Type", "text/plain"),
            ("Content-Length", str(len(data)))
        ])
        return iter([data])

To run the server:

gunicorn -w 4 myapp:app

Executing the above command will only run the development server. In the next section we will explain how to deploy a Gunicorn

Deploying a Gunicorn server

This is the official page. It doesn't explain well how to do it:

http://docs.gunicorn.org/en/latest/deploy.html

This tutorial explain well hot to do deploy a Flask Applications with Gunicorn and Nginx:

https://www.digitalocean.com/community/tutorials/how-to-serve-flask-applications-with-gunicorn-and-nginx-on-ubuntu-16-04

Now, when using Dash, we have to make a few changes with respect to the above tutorial. The following posts helped me to find the solution:

https://community.plot.ly/t/error-with-gunicorn/8247

https://community.plot.ly/t/failed-to-find-application-object-server-in-app/13723

Example - Deploying a Dash aplications with Gunicorn and Nginx on Ubuntu 16.04 (based on https://www.digitalocean.com/community/tutorials/how-to-serve-flask-applications-with-gunicorn-and-nginx-on-ubuntu-16-04)

Create and activate a Python Virtual Environment :

sudo pip3 install virtualenv

mkdir ~/myproject
cd ~/myproject

virtualenv myprojectenv  # This will install a local copy of Python and pip into a directory called myprojectenv

source myprojectenv/bin/activate

Your prompt will change to indicate that you are now operating within the virtual environment. It will look something like this:

(myprojectenv)user@host:~/myproject$.

Install Flask, Dash and Gunicorn inside the virtual environment:

pip install gunicorn flask

ver «Dash» installation
ver «gunicorn» installation

Create a Sample App:

import os
import dash
import dash_core_components as dcc
import dash_html_components as html

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash(__name__, external_stylesheets=external_stylesheets)

server = app.server

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

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

    dcc.Graph(
        id='example-graph',
        figure={
            'data': [
                {'x': [1, 2, 3], 'y': [4, 1, 2], 'type': 'bar', 'name': 'SF'},
                {'x': [1, 2, 3], 'y': [2, 4, 5], 'type': 'bar', 'name': u'Montréal'},
            ],
            'layout': {
                'title': 'Dash Data Visualization'
            }
        }
    )
])

if __name__ == '__main__':
    app.run_server(debug=True, host='0.0.0.0')

Notice that we have included: server = app.server.

Now, you can test your Dash app by typing:

(myprojectenv)$ python myproject.py

Visit your server's domain name or IP address followed by :port in your web browser to verify your App is working.

Create the WSGI Entry Point: We'll create a file that will serve as the entry point for our application. This will tell our Gunicorn server how to interact with the application:

(myprojectenv)$ vi ~/myproject/wsgi.py

from myproject import server

if __name__ == "__main__":
    server.run()

Notice that we have import the variable server from myproject.py

This is the different with respect to a pure Flask application, where you would import App instead of server. In Dash, we require app.server, which is in the server variable we have created. So if we were deploying a pure flak App, it would be:

from myproject import app

if __name__ == "__main__":
    app.run()

Testing Gunicorn's Ability to Serve the Project:

(myprojectenv)$ cd ~/myproject
(myprojectenv)$ gunicorn --bind 0.0.0.0:5000 wsgi:server

For a pure Flask application, would be wsgi:App.

Visit your server's domain name or IP address with :port appended to the end in your web browser again.

We're now done with our virtual environment, so we can deactivate it:

(myprojectenv)$ deactivate

Any Python commands will now use the system’s Python environment again.

Create a systemd Unit File:

$ vi /etc/systemd/system/myproject.service

[Unit]
Description=Gunicorn instance to serve myproject
After=network.target

[Service]
User=root
Group=www-data
WorkingDirectory=/root/myproject
Environment="PATH=/root/myproject/myprojectenv/bin"
ExecStart=/root/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007 wsgi:server

[Install]
WantedBy=multi-user.target

We can now start the Gunicorn service we created and enable it so that it starts at boot:

$ sudo systemctl start myproject
$ sudo systemctl enable myproject

Configuring Nginx to Proxy Requests:

$ vi /etc/nginx/sites-available/default

server {
    listen 80;
    server_name gofaaaz.sinfronteras.ws;

    location / {
        include proxy_params;
        proxy_pass http://unix:/root/myproject/myproject.sock;
    }
}

Finally, we restart the Nginx process:

sudo systemctl restart nginx.service

You should now be able to go to your server's domain name or IP address in your web browser and see your App.

Dash Layout

https://dash.plot.ly/getting-started

Dash apps are composed of two parts:

The first part is' the "layout" of the app and it describes what the application looks like.
The second part describes the interactivity of the application and will be covered in the next chapter.

Dash provides Python classes for all of the visual components of the application. We maintain a set of components in the dash_core_components and the dash_html_components library but you can also build your own with JavaScript and React.js.

To get started, create a file named 'app.py' with the following code:

import dash
import dash_core_components as dcc
import dash_html_components as html


app = dash.Dash(__name__)

app.layout = html.Div(children=[
    html.H1(children='Hello Dash'),
    html.Div(children='Dash: A web application framework for Python')
])


if __name__ == '__main__':
    app.run_server(debug=True, port=8551)

Es importante utilizar un port que no esté ocupado por otro proceso.

Including style:

import dash 
import dash_core_components as dcc
import dash_html_components as html

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash(__name__,external_stylesheets=external_stylesheets)

colors = {
    'backgroud': '#111111',
    'text': '#7FDBFF'
}

app.layout = html.Div(
    style={
        'backgroundColor': colors['backgroud']
    },
    children=[
        html.H1(
            style={
                'textAlign': 'center',
                'color': colors['text']
            },
            children='Hello Dash'
        ),
        html.Div(
            style={
                'textAlign': 'center',
                'color': colors['text']
            },
            children='Dash: A web application framework for Python'
        ),
        dcc.Graph(
            id='example-graph',
            figure={
                'data': [
                    {'x': [1, 2, 3], 'y': [4, 1, 2], 'type': 'bar', 'name': 'SF'},
                    {'x': [1, 2, 3], 'y': [2, 4, 5], 'type': 'bar', 'name': u'Montréal'},
                ],
                'layout': {
                    'title': 'Dash Data Visualisation',
                    'plot_bgcolor': colors['backgroud'],
                    'paper_bgcolor': colors['backgroud'],
                    'font': {
                        'color': colors['text']
                    }
                }
            }
        )
    ]
)

if __name__ == '__main__':
    app.run_server(debug=True, port=8551)

Dash - Plotly

Contents

Word cloud

Installation

Minimal example

Dash

Installation

Examples

Example 2

Deploying Dash Apps

Flask Deployment

Gunicorn

Deploying a Gunicorn server

Dash Layout

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