Show Matplotlib in Flask

To show a plot in Flask, we can take the following steps−

• Make a small application.
• To run Flask application, go to the current directory.
• $ export FLASK_APP=file.py
• $ flask run
• Open the browser, hit url:http://127.0.0.1:5000/print-plot/
• To plot the figure, we can create data points for x and y using random.
• Plot data points, x and y, on the created axis.
• Write a figure into png figure format.
• Retrieve the entire contents of the BytesIO object.

Example

import io
from flask import Response
from matplotlib.backends.backend_agg import FigureCanvasAgg as FigureCanvas
from matplotlib.figure import Figure
from flask import Flask
import numpy as np
plt.rcParams["figure.figsize"] = [7.50, 3.50]
plt.rcParams["figure.autolayout"] = True
app = Flask(__name__)
@app.route('/print-plot')
def plot_png():
   fig = Figure()
   axis = fig.add_subplot(1, 1, 1)
   xs = np.random.rand(100)
   ys = np.random.rand(100)
   axis.plot(xs, ys)
   output = io.BytesIO()
   FigureCanvas(fig).print_png(output)
   return Response(output.getvalue(), mimetype='image/png')

Output