Use Dash to Build to Web Apps on CouchDB Data

The rich ecosystem of Python modules lets you get to work quickly and integrate your systems more effectively. With the CData Python Connector for CouchDB, the pandas module, and the Dash framework, you can build CouchDB-connected web applications for CouchDB data. This article shows how to connect to CouchDB with the CData Connector and use pandas and Dash to build a simple web app for visualizing CouchDB data.

With built-in, optimized data processing, the CData Python Connector offers unmatched performance for interacting with live CouchDB data in Python. When you issue complex SQL queries from CouchDB, the driver pushes supported SQL operations, like filters and aggregations, directly to CouchDB and utilizes the embedded SQL engine to process unsupported operations client-side (often SQL functions and JOIN operations).

Connecting to CouchDB Data

Connecting to CouchDB data looks just like connecting to any relational data source. Create a connection string using the required connection properties. For this article, you will pass the connection string as a parameter to the create_engine function.

Set the following to connect:

• Url: The Url of your instance. For example: http://localhost:5984
• User The Apache CouchDB user account used to authenticate.
• Password The Apache CouchDB password associated with the authenticating user.

After installing the CData CouchDB Connector, follow the procedure below to install the other required modules and start accessing CouchDB through Python objects.

Install Required Modules

Use the pip utility to install the required modules and frameworks:

pip install pandas
pip install dash
pip install dash-daq

Visualize CouchDB Data in Python

Once the required modules and frameworks are installed, we are ready to build our web app. Code snippets follow, but the full source code is available at the end of the article.

First, be sure to import the modules (including the CData Connector) with the following:

import os
import dash
import dash_core_components as dcc
import dash_html_components as html
import pandas as pd
import cdata.apachecouchdb as mod
import plotly.graph_objs as go

You can now connect with a connection string. Use the connect function for the CData CouchDB Connector to create a connection for working with CouchDB data.

cnxn = mod.connect("Url=http://localhost:5984;User=abc123;Password=abcdef;")

Execute SQL to CouchDB

Use the read_sql function from pandas to execute any SQL statement and store the result set in a DataFrame.

df = pd.read_sql("SELECT MovieRuntime, MovieRating FROM Movies WHERE MovieRating = 'R'", cnxn)

Configure the Web App

With the query results stored in a DataFrame, we can begin configuring the web app, assigning a name, stylesheet, and title.

app_name = 'dash-apachecouchdbedataplot'

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

app = dash.Dash(__name__, external_stylesheets=external_stylesheets)
app.title = 'CData + Dash'

Configure the Layout

The next step is to create a bar graph based on our CouchDB data and configure the app layout.

trace = go.Bar(x=df.MovieRuntime, y=df.MovieRating, name='MovieRuntime')

app.layout = html.Div(children=[html.H1("CData Extension + Dash", style={'textAlign': 'center'}),
	dcc.Graph(
		id='example-graph',
		figure={
			'data': [trace],
			'layout':
			go.Layout(title='CouchDB Movies Data', barmode='stack')
		})
], className="container")

Set the App to Run

With the connection, app, and layout configured, we are ready to run the app. The last lines of Python code follow.

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

Now, use Python to run the web app and a browser to view the CouchDB data.

python apachecouchdb-dash.py

Free Trial & More Information

Download a free, 30-day trial of the CData Python Connector for CouchDB to start building Python apps with connectivity to CouchDB data. Reach out to our Support Team if you have any questions.

Full Source Code

import os
import dash
import dash_core_components as dcc
import dash_html_components as html
import pandas as pd
import cdata.apachecouchdb as mod
import plotly.graph_objs as go

cnxn = mod.connect("Url=http://localhost:5984;User=abc123;Password=abcdef;")

df = pd.read_sql("SELECT MovieRuntime, MovieRating FROM Movies WHERE MovieRating = 'R'", cnxn)
app_name = 'dash-apachecouchdbdataplot'

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

app = dash.Dash(__name__, external_stylesheets=external_stylesheets)
app.title = 'CData + Dash'
trace = go.Bar(x=df.MovieRuntime, y=df.MovieRating, name='MovieRuntime')

app.layout = html.Div(children=[html.H1("CData Extension + Dash", style={'textAlign': 'center'}),
	dcc.Graph(
		id='example-graph',
		figure={
			'data': [trace],
			'layout':
			go.Layout(title='CouchDB Movies Data', barmode='stack')
		})
], className="container")

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