stop / start / pause in python matplotlib animation

Question

I’m using FuncAnimation in matplotlib’s animation module for some basic animation. This function perpetually loops through the animation. Is there a way by which I can pause and restart the animation by, say, mouse clicks?

Asked By: Jaco Vermaak

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Source

Answer 1

Here is a FuncAnimation example which I modified to pause on mouse clicks.
Since the animation is driven by a generator function, simData, when the global variable pause is True, yielding the same data makes the animation appear paused.

The value of paused is toggled by setting up an event callback:

def onClick(event):
    global pause
    pause ^= True
fig.canvas.mpl_connect('button_press_event', onClick)

import matplotlib.pyplot as plt
import numpy as np
import matplotlib.animation as animation

pause = False
def simData():
    t_max = 10.0
    dt = 0.05
    x = 0.0
    t = 0.0
    while t < t_max:
        if not pause:
            x = np.sin(np.pi*t)
            t = t + dt
        yield x, t

def onClick(event):
    global pause
    pause ^= True

def simPoints(simData):
    x, t = simData[0], simData[1]
    time_text.set_text(time_template%(t))
    line.set_data(t, x)
    return line, time_text

fig = plt.figure()
ax = fig.add_subplot(111)
line, = ax.plot([], [], 'bo', ms=10)
ax.set_ylim(-1, 1)
ax.set_xlim(0, 10)

time_template = 'Time = %.1f s'
time_text = ax.text(0.05, 0.9, '', transform=ax.transAxes)
fig.canvas.mpl_connect('button_press_event', onClick)
ani = animation.FuncAnimation(fig, simPoints, simData, blit=False, interval=10,
    repeat=True)
fig.show()

Answered By: unutbu

Answer 2

This works…

anim = animation.FuncAnimation(fig, animfunc[,..other args])

#pause
anim.event_source.stop()

#unpause
anim.event_source.start()

Answered By: fred

Answer 3

Combining both the answers from @fred and @unutbu here, we can add an onClick function after creating the animation:

import matplotlib.pyplot as plt
import matplotlib.animation as animation

fig = plt.figure()

def run_animation():
    anim_running = True

    def onClick(event):
        nonlocal anim_running
        if anim_running:
            anim.event_source.stop()
            anim_running = False
        else:
            anim.event_source.start()
            anim_running = True

    def animFunc( ...args... ):
        # Animation update function here

    fig.canvas.mpl_connect('button_press_event', onClick)

    anim = animation.FuncAnimation(fig, animFunc[,...other args])

run_animation()

Now we can simply stop or start the animation with clicks.

Answered By: woodenflute

Answer 4

I landed on this page trying to implement the same functionality, pausing matplotlibs animation. The other answers are great, but in addition I wanted to be able to manually loop through the frames using the arrow keys. For anyone looking for the same functionality, here’s my implementation:

import matplotlib.pyplot as plt
import matplotlib.animation as ani

fig, ax = plt.subplots()
txt = fig.text(0.5,0.5,'0')

def update_time():
    t = 0
    t_max = 10
    while t<t_max:
        t += anim.direction
        yield t

def update_plot(t):
    txt.set_text('%s'%t)
    return txt

def on_press(event):
    if event.key.isspace():
        if anim.running:
            anim.event_source.stop()
        else:
            anim.event_source.start()
        anim.running ^= True
    elif event.key == 'left':
        anim.direction = -1
    elif event.key == 'right':
        anim.direction = +1

    # Manually update the plot
    if event.key in ['left','right']:
        t = anim.frame_seq.next()
        update_plot(t)
        plt.draw()

fig.canvas.mpl_connect('key_press_event', on_press)
anim = ani.FuncAnimation(fig, update_plot, frames=update_time,
                         interval=1000, repeat=True)
anim.running = True
anim.direction = +1
plt.show()

Some notes:

To be able to modify the values of running and direction, I assigned them to anim. It avoids using nonlocal (not avaible in Python2.7) or global (not desirable since I’m running this code within another function). Not sure whether this is good practice, but I found it quite elegant.
For the manual update, I’m accessing anim‘s generator object that FuncAnimation uses to update the plot. This ensures that when I resume the animation, it starts from the active frame rather than from where it was originally paused.

Answered By: Peter9192

Answer 5

Since there are quite a few comments on different answers asking for documented feature, I dug deeper based on fred’s answer. It seems to work, but since matplotlib 3.4.0 there are new functions to pause and resume plotting: pause() and resume(). They call event_source.stop() and start() internally, but they also pause animation altogether, which may reduce the hardware strain.

They can be called on any matplotlib.animation.Animation object, including FuncAnimation subclass.

Answered By: Yksisarvinen

stop / start / pause in python matplotlib animation

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