Matplotlib animation either freezes after a few fr

Question

I've been trying for hours to get this simple script working, but nothing I do seems to help. It's a slight modification of the most basic animated plot sample code from the Matplotlib website, that should just show a few frames of noise (I have the same issue with the unmodified code from their website BTW).

On my computer with the TkAgg backend I get about 20 frames (out of 60) before the plot window freezes. With Qt4Agg I just get a frozen, black window and no frames at all are plotted. I've tried multiple combinations of different NumPy, PyQt, Python and Matplotlib versions, but always get the same result.

Please let me know if this works for you or if anything looks wrong. I'm pretty sure this did work in the past, so I'm thinking it may be a Windows issue or something related to ion().

FYI I'm using Windows 7 (32 bit) and I've tested with Python 2.6/2.7, MPL 1.0.0/0.9.9.8, PyQt 4.6/4.7, Numpy 1.4/1.5b.

import matplotlib
matplotlib.use('TkAgg') # Qt4Agg gives an empty, black window
from pylab import *
import time

ion()
hold(False)

# create initial plot
z = zeros(10)
line, = plot(z)
ylim(-3, 3)

for i in range(60):
    print 'frame:', i

    d = randn(10)
    line.set_ydata(d)

    draw()
    time.sleep(10e-3)

This simpler version also freezes after the first couple frames:

from pylab import *

ion()
hold(False)

for i in range(40):
    plot(randn(10))
    draw()

show()

Thanks!

EDIT: These people seem to be having the same or a similar problem as me:

• mail-archive.com/[e-mail]/msg10844.html
• stackoverflow.com/questions/2604119/matplotlib-pyplot-pylab-not-updating-figure-while-isinteractive-using-ipython
• mail-archive.com/[e-mail]/msg01283.html

Doesn't look like any of them were able to fix it either :(

Answer 1

I was having (I think) the same trouble, where the window would freeze if I took the focus off it or tried to drag it around, using Python 2.7 on Windows 7 with Matplotlib 1.3, and TKAgg backend. I had a call to time.sleep(1) in my main while loop, and when I replaced that with plt.pause(1), that fixed the problem. So, try and use matplotlib's pause function rather than time module sleep function, it worked for me.