Matplotlib and Jupyter Notebooks: new plot outputted per loop iteration

Question

There are a lot of questions regarding how to use matplotlib, especially for how to either update or output a new chart per loop iteration. In particular this question is in relation to matplotlib and jupyter-notebook

For example:

Use a loop to plot n charts Python

The answer is as follows:

import matplotlib.pyplot as plt
x=[[1,2,3,4],[1,2,3,4],[1,2,3,4],[1,2,3,4]]
y=[[1,2,3,4],[1,2,3,4],[1,2,3,4],[1,2,3,4]]
for i in range(len(x)):
    plt.figure()
    plt.plot(x[i],y[i])

which appears to work...

until we add anything else:

for example, add a sleep statement after each plot:

import matplotlib.pyplot as plt
from time import sleep
x=[[1,2,3,4],[1,2,3,4],[1,2,3,4],[1,2,3,4]]
y=[[1,2,3,4],[1,2,3,4],[1,2,3,4],[1,2,3,4]]
for i in range(len(x)):
    plt.figure()
    plt.plot(x[i],y[i])
    sleep(2)

and suddenly it doesn't work.

One can also use any form of print to see the same issue

import matplotlib.pyplot as plt
from time import sleep
x=[[1,2,3,4],[1,2,3,4],[1,2,3,4],[1,2,3,4]]
y=[[1,2,3,4],[1,2,3,4],[1,2,3,4],[1,2,3,4]]
for i in range(len(x)):
    plt.figure()
    plt.plot(x[i],y[i])
    print('loop: ', i)

So how can I print out a new plot for each loop in a jupyter-notebook?

What exactly "does not work"? If running the above, the result is as expected and four plots are shown. — ImportanceOfBeingErnest
– ImportanceOfBeingErnest, Commented Nov 17, 2017 at 13:42
@ImportanceOfBeingErnest yes, the four plots are made, which is fine. I want them to output during the loop iterations. As it stands, the four plots are rendered after the computation ends — SumNeuron
– SumNeuron, Commented Nov 17, 2017 at 14:33

GenError · Accepted Answer · 2019-09-08 08:11:10Z

1

You have to call plt.pause(1) after each iteration to tell matplotlib to pause for 1 second and redraw the figures (https://matplotlib.org/3.1.1/api/_as_gen/matplotlib.pyplot.pause.html)

import matplotlib.pyplot as plt
x=[[1,2,3,4],[1,2,3,4],[1,2,3,4],[1,2,3,4]]
y=[[1,2,3,4],[1,2,3,4],[1,2,3,4],[1,2,3,4]]
for i in range(len(x)):
    plt.figure()
    plt.plot(x[i],y[i])
    plt.pause(1)

Now the figures are drawn after each iteration.

answered Sep 8, 2019 at 8:11

GenError

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