Figure GUI freezing

Question

I am fairly new in python, and I am trying to have a plot, based on data stored in a file. This file may be updated at any time, so I am trying to make the drawing updated e

Answer 1

On top of the answer of @tcaswell (that solve the problem), I suggest to rethink the script in a more OO way.

I have tried this:

plt.ion()
plt.figure()
plt.show()

while True:
    x=np.arange(10)
    y=np.random.rand(10)

    plt.subplot(121)
    plt.plot(x,y)
    plt.subplot(122)        
    plt.plot(x,2*y)

    plt.draw()

    plt.pause(3)

but it does not work (it looks like it opens a gui at plt.figure and then at each loop.

A solution like this:

plt.ion()
fig, ax = plt.subplots(nrows=2, ncols=1)
plt.show()

while True:
    x=np.arange(10)
    y=np.random.rand(10)

    ax[0].plot(x,y)
    ax[1].plot(x,2*y)

    plt.draw()

    plt.pause(3)

is much more efficient (axes are created only once), neater (at the end matplotlib is OO) and potentially less prone to memory leaks.

Besides, from your most I gather that at each loop you read in the files again and then plot the new lines. If this is the case, you want to clear first the content of the axes before redrawing. In my simple case you can clear the axes with

for a in ax:
    a.clear()

Answer 2

You want to use the plt.pause(3) function instead of time.sleep(). pause includes the necessary calls to the gui main loop to cause the figure to re-draw.

also see: Python- 1 second plots continous presentation, matplotlib real-time linear line, pylab.ion() in python 2, matplotlib 1.1.1 and updating of the plot while the program runs,