Pausing matplotlib animation on program starts

Question

When the program starts, I want to open a window with animation, but it must be paused from the beggining.

I tried to edit the example from https://matplotlib.org/stable/gallery/animation/pause_resume.html.

from matplotlib import pyplot as plt

import matplotlib.animation as animation

import numpy as np



class PauseAnimation:
    def __init__(self):
        fig, ax = plt.subplots()

        x = np.linspace(-0.1, 0.1, 1000)

        # Start with a normal distribution
        self.n0 = (1.0 / ((4 * np.pi * 2e-4 * 0.1) ** 0.5) * np.exp(-x ** 2 / (4 * 2e-4 * 0.1)))
        self.p, = ax.plot(x, self.n0)

        self.animation = animation.FuncAnimation(fig, self.update, frames=200, interval=50, blit=True)

        self.animation.pause()  # not working
        self.animation.event_source.stop()  # not working

        self.paused = True

        fig.canvas.mpl_connect('button_press_event', self.toggle_pause)

    def toggle_pause(self, *args, **kwargs):
        if self.paused:
            self.animation.resume()
        else:
            self.animation.pause()
        self.paused = not self.paused

    def update(self, i):
        self.n0 += i / 100 % 5
        self.p.set_ydata(self.n0 % 20)
        return self.p,


pa = PauseAnimation()
plt.show()

I added self.animation.pause() and self.animation.event_source.stop(), but it seems no effect, animation is still playing. How can I implement this?

Answer 1

To be able to pause the animation you need that the main loop is already running, that is to say, that show has already been called.

A very simple solution is instead of pausing the animation at startup, just don't start it, for example:

import matplotlib.pyplot as plt
import numpy as np

import matplotlib.animation as animation

class PauseAnimation:
    def __init__(self):
        self.fig, ax = plt.subplots()

        x = np.linspace(-0.1, 0.1, 1000)

        # Start with a normal distribution
        self.n0 = (1.0 / ((4 * np.pi * 2e-4 * 0.1) ** 0.5) * np.exp(-x ** 2 / (4 * 2e-4 * 0.1)))
        self.p, = ax.plot(x, self.n0)
        
        self.paused = True
        self.animation = None
        
        self.fig.canvas.mpl_connect('button_press_event', self.toggle_pause)


    def toggle_pause(self, *args, **kwargs):
        if self.animation is None:
            self.animation = animation.FuncAnimation(
                self.fig, self.update, frames=200, interval=50, blit=True)
        if self.paused:
            self.animation.resume()
        else:
            self.animation.pause()
        self.paused = not self.paused

    def update(self, i):
        self.n0 += i / 100 % 5
        self.p.set_ydata(self.n0 % 20)
        return self.p,


pa = PauseAnimation()
plt.show()