Updating a matplotlib plot is straightforward. Create the data, the plot and update in a loop. Setting interactive mode on is essential: plt.ion(). This controls if the figure is redrawn every draw() command. If it is False (the default), then the figure does not update itself. Related courses:

• Practice Python with interactive exercises
• Practice Python with interactive exercises

Update plot example Copy the code below to test an interactive plot.

import matplotlib.pyplot as plt
import numpy as np
x = np.linspace(0, 10*np.pi, 100)
y = np.sin(x)
plt.ion()
fig = plt.figure()
ax = fig.add_subplot(111)
line1, = ax.plot(x, y, 'b-')
for phase in np.linspace(0, 10*np.pi, 100):
line1.set_ydata(np.sin(0.5 * x + phase))
fig.canvas.draw()

Capture of a frame of the program above

Explanation We create the data to plot using:

x = np.linspace(0, 10*np.pi, 100)
y = np.sin(x)

Turn on interacive mode using:

plt.ion()

Configure the plot (the 'b-' indicates a blue line):

fig = plt.figure()
ax = fig.add_subplot(111)
line1, = ax.plot(x, y, 'b-')

And finally update in a loop:

for phase in np.linspace(0, 10*np.pi, 100):
line1.set_ydata(np.sin(0.5 * x + phase))
fig.canvas.draw()