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Building a Dash App with Plotly Graph Updates and Live Web Socket Streaming
As a trader, you want to stay up-to-date with real-time market data. One effective way to do this is to create a live streaming dashboard using Dash, a popular Python library for building web applications. In this article, we will show you how to build a Dash app that feeds live data from the Ethereum blockchain and updates a Plotly graph in real time.
Prerequisites
Before you begin, make sure you have the following installed:
- Dash (“pip install dash”)
- Plotly (“pip install plotly”)
- Python 3.x
Set up the environment
Create a new Python file (e.g. “app.py”) and add the following code to set up the environment:
import dash
from dash import dcc, html
import plotly.graph_objects as go
import websocket
Initialize the Dash applicationapplication = dash.Dash(__name__)
Set up the Plotly graphfig = go.Figure(data=[go.Scatter(x=[], y=[])])
Create the Plotly componentplotly_component = dcc.Graph(id='live-websocket-graph')
Create the trading bot
Then create a new file (e.g. “trading_bot.py”) that contains the logic for your trading bot. In this example, we will use a simple Ethereum blockchain node to get live data:
import eth_utils
from eth_positioning import BlockNumber
Set up an Ethereum blockchain nodenode_url = '
eth_node = ' + node_url
def get_block_number():
block_number = BlockNumber.from_string('1')
return block_number.to_int()
app.layout = html.Div([
html.H1 (Ethereum Live Stream Dashboard),
dcc.Graph(id='live-websocket-graph'),
dcc.LiveSocket(url=node_url, id='live-websocket-socket', stream=True),
])
def update_graph():
Get live data from an Ethereum blockchain nodeblock_number = get_block_number()
block_data = eth_utils.get_block(block_number).get_value()
Update the Plotly graph with new datafig.data[0].x.extend(block_number)
fig.data[0].y.extend([block_data])
Redraw the graphapp.update_graph(id='live-websocket-graph', layout=fig.layout)
@app.callback(
[html.Button('Refresh data', id='refresh-data-button')],
[dash.dependencies.Output('live-websocket-socket-stream', 'data'), dash.dependencies.Output('live-websocket-socket-stream', 'figure')]
)
def refresh_data_button():
Get new data from Ethereum blockchain nodeblock_number = get_block_number()
Update the Plotly graph with the new datafig.update_layout(x=[block_number], y=[])
return html.P('Data updated successfully!'), fig
if __name__ == '__main__':
app.run_server(debug=True)
Run the application
To run the application, run the following command:
python app.py
This will start the Dash server and open a web browser with the dashboard.
Live Streaming Data
Now that you have set up the live streaming data, update the graph by clicking the 'Refresh Data' button. This will update the Plotly graph with the new data received from the Ethereum blockchain node.
To visualize this in more detail, you can use Dash’s built-in dash_core_components library to create a dashboard with several interactive elements:
“ python
import dash_core_components as dcc
from dash import html
Create the dashboard
app = dash.Dash(__name__)
Add widgets to the dashboard
app.layout = html.Div([
html.H1 (Ethereum Live Stream Dashboard),
dcc.Graph(id=’live-websocket-graph’),
dcc.LiveSocket(id=’live-websocket-socket’, stream=True),
])
@app.callback(
[html.Button(‘Refresh Data’, id=’refresh-data-button’)],
[dash.dependencies.Output(‘live-websocket-socket-stream’, ‘data’), dash.dependencies.