Matplotlib figure does not update in every loop-CodePudding

I would like to update a figure of matplotlib for every iteration in a loop. It works for about the first 30 iterations, but then the updates stop although there are more iterations.

Following you can find my code for the figure:

import numpy as np
import matplotlib.pyplot as plt


class SimpOutput:
    fig = None
    ax_l = None
    ax_r = None

    it_container = []
    obj_container = []

    def __init__(self):
        self.fig, (self.ax_l, self.ax_r) = plt.subplots(nrows=1, ncols=2, figsize=(8, 4))
        self.ax_l.set_title("Flexibility $c$")
        self.ax_l.set_ylabel("obj. value $c$")
        self.ax_l.set_xlabel("Iteration")

        self.ax_r.set_title("Shape")

        self.fig.show()

    def update(self, iteration, obj, x):

        self.it_container.append(iteration)
        self.obj_container.append(obj)

        self.ax_l.plot(self.it_container, self.obj_container, c="r")

        x = x.reshape((4, 4))
        x = x.T
        x = np.flip(x, 0)
        self.ax_r.imshow(x, cmap="binary")
        plt.pause(0.1)
        self.fig.show()
        plt.pause(0.1)

if __name__ == "__main__":
    out = SimpOutput()

    for i in range(50):

        out.update(i, 1000 * np.random.rand(), np.random.rand(16))

update is called in every loop.

Using fig.canvas.show() and different values for pause does not affect on the update. Furthermore, the methods set_array() and set_data() do not fix the problem either. While debugging, the figure is updated for every iteration. I write the code with PyCharm.

Does anyone had the same issue or rather does anyone has an idea how to solve this issue?

Thanks in advance!

Bests,

Sebastian

CodePudding user response：

I tried to run the following simple code:

for i in range(50):
    plt.clf()
    pd.DataFrame([3,4,i]).plot.line(title=f'iteration {i}')
    plt.show()

Not updating any figure, just clearing the old one and plotting a new figure.

It stops creating new figures after 30 iterations as well. Same problem as you.

I suspected the problem is in pycharm, so I tried one more thing.

I replaced plt.show() with plt.savefig(f'example_{i}.jpg'). It indeed saved all 50 figures in the folder (means it worked okay), and in addition, it gave me a warning:

envs\my_main_env\lib\site-packages\pandas\plotting\_matplotlib\core.py:337: RuntimeWarning: More than 20 figures have been opened. Figures created through the pyplot interface (`matplotlib.pyplot.figure`) are retained until explicitly closed and may consume too much memory. (To control this warning, see the rcParam `figure.max_open_warning`).
  fig = self.plt.figure(figsize=self.figsize)

indicating the problem is in the number of figures open at parallel. You can google the warning find some answers to it (e.g. warning about too many open figures).

I added the parameter at the beginning of the code: plt.rcParams.update({'figure.max_open_warning': 60})

now, running again. In pycharm in scientific mode, it didn't work. So I turned off scientific mode (opening a new figure for each plot) and now it works well! so I think that the limitation is a pycharm limitation for scientific mode - how many figures can be open at the same time.

turn off scientific mode for plotting by going to Settings->Tools->Python Scientific-> uncheck "Show plots in tool window" box.

That worked for me. I don't know how to change the limit in scientific mode (if possible at all). I believe it gives enough insights for you to solve your issue - whether by saving the figures or by plotting them without scientific mode.