Make interactive matplotlib window not pop to front on each update (Windows 7)

Question

Today I upgraded matplotlib to version 2.0.2, after not upgrading for possibly 3 years.

Now I have the problem that in interactive plots the window always comes to t

Answer 1

Changing the backend

The issue seems only present using the Tk backend. Using the Qt backend, the window would stay where it was while updating with plt.pause.

To change the backend use those lines at the beginning of your script.

import matplotlib
matplotlib.use("Qt4agg") # or "Qt5agg" depending on you version of Qt

Modifying plt.pause

If changing the backend is not an option, the following might help. The cause of the window constantly popping up to the front comes from plt.pause calling plt.show() internally. You therefore implement you own pause function, without calling show. This requires to be in interactive mode plt.ion() first and then at least once call plt.show(). Afterwards you may update the plot with the custom mypause function as shown below.

import matplotlib
matplotlib.use("TkAgg")
import matplotlib.pyplot as plt
from time import time
from random import random

plt.ion()
# set up the figure
fig = plt.figure()
plt.xlabel('Time')
plt.ylabel('Value')

plt.show(block=False)

def mypause(interval):
    backend = plt.rcParams['backend']
    if backend in matplotlib.rcsetup.interactive_bk:
        figManager = matplotlib._pylab_helpers.Gcf.get_active()
        if figManager is not None:
            canvas = figManager.canvas
            if canvas.figure.stale:
                canvas.draw()
            canvas.start_event_loop(interval)
            return


t0 = time()
t = []
y = []
while True:
    t.append( time()-t0 )
    y.append( random() )
    plt.gca().clear()
    plt.plot( t , y )
    mypause(1)

Using an animation.

Finally, using a matplotlib.animation class would render all of the above obsolete. An example for matplotlib.animation.FuncAnimation is shown on the matplotlib page.

Answer 2

I had the same problem on the Mac. I'm not sure if this is the best approach, but instead of using plt.pause(0.001), I switched to fig.canvas.start_event_loop(0.001) to update each frame on my animation. This allows the windows to stay in the background.

Answer 3

It is April 2019 and the mypause() function (copied from the upto date pyplot implementation) for Matplotlib 3.0.3 should look more like

import time
import matplotlib.pyplot as plt
def mypause(interval):
    manager = plt._pylab_helpers.Gcf.get_active()
    if manager is not None:
        canvas = manager.canvas
        if canvas.figure.stale:
            canvas.draw_idle()        
        #plt.show(block=False)
        canvas.start_event_loop(interval)
    else:
        time.sleep(interval)

After some testing (Qt5 backend/Spyder/Windows 7 64bit) the calls that do the trick for me are:

#plt.pause(0.001) #Brings plot to foreground
#fig.canvas.draw() #Does not work
#plt.draw_all() #Does not work
#plt.draw() #Does not work
#fig.canvas.flush_events() #Updates only if I click the figure 
#import time; time.sleep(0.001) #Does not help flush_events()
#fig.canvas.draw_idle() #Does not work by itself
#fig.canvas.start_event_loop(0.001) #Does not work by itself
#mypause(0.001) #Works!

#Works!
fig.canvas.draw_idle()
fig.canvas.start_event_loop(0.001)

Were fig is your figure object. Either of both alone didn't work in my case. According to the animation documentation this is essentially what FuncAnimation does.

Answer 4

I rewrote the code to use matplotlib.animation with the help from this documentation page https://matplotlib.org/devdocs/api/animation_api.html#module-matplotlib.animation

I got to that page through this one https://matplotlib.org/devdocs/api/_as_gen/matplotlib.pyplot.pause.html

which states the following about matplotlib.pyplot.pause

This can be used for crude animation. For more complex animation, see matplotlib.animation.

This function is experimental; its behavior may be changed or extended in a future release.