Matplotlib doesn't open Plotting window when ploting in a cycle

Question

I want to plot some data live so I tried this simple example:

import time
import numpy as np
import matplotlib.pyplot as plt

plt.axis([0, 1000, 0, 1])
plt.ion()
plt.show()

for i in range(1000):
    print "in"
    y = np.random.random()
    plt.scatter(i, y)
    plt.draw()
    time.sleep(0.05)

The plotting window simply opens up, but nothing is ploted on it (the window actually stops responding). I notices it is indeed performing the for cycle since i can se the "in" print output

Hello @threxx , i did that but it actually doesnt work. Only a bunch of fempty pop up. If i indicate which figure to plot int (i.e. plt.figure(1)), still, nothing happens — David Alvarez
– David Alvarez, Commented Jan 26, 2016 at 8:32

Marek · Accepted Answer · 2016-01-25 22:10:55Z

2

I've met problems with Python3 with in-time drawing.
This should work for you.

import numpy as np
import matplotlib.pyplot as plt

plt.axis([0, 1000, 0, 1])
plt.ion()
plt.show()

for i in range(1000):
    print "in"
    y = np.random.random()
    plt.scatter(i, y)
    plt.pause(0.05)

answered Jan 25, 2016 at 22:10

Marek

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2 Comments

tacaswell Over a year ago

The reason that pause works where as sleep does not is that pause runs the GUI event loop as well.

David Alvarez Over a year ago

@tcaswell , what do you mean by " pause runs the GUI event loop as well "

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