Create an animation with varied time interval in python

Question

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt 
import matplotlib.animation as animation
fig, ax = plt.subplots(figsize=(3,9))
dot, = ax.plot([], [], 'ro')

def init():
    ax.set_xlim(0,1)
    ax.set_ylim(0,3)
    return

def gen_dot():
    for i in range(len(list_x_y)):
    newdot = list_x_y[i]
    yield newdot

def update_dot(newd):
    dot.set_data(newd[0],newd[1])
    return dot

ani = animation.FuncAnimation(fig, update_dot, frames = gen_dot, interval = 100, 
init_func=init)
ani.save('Steps.gif',writer='imagemagick',fps=24)
plt.show()

Hey Guys, So I was trying to create an animation mimicking a real person walking a treadmill with the code shown above. The thing is, I need a variable time interval so that the person is not working at a constant speed, which is not realistic at all.

I figured that probably animation function does not support a varied time interval functionality so I tried using a For loop and get a time interval list such that each time in the for loop it will sleep for a specific amount of time and continue...However, JupyterNotebook will not refresh the frames as I intended it to be, creating a static image in the end of the period...Is there any way I can create a gif with varied time interval? I think maybe I can save all the frames and use imageio to create a gif...But does imageio take varied time interval as input as well? I'm struggling with this problems for hours...Any help would be appreciated. Thanks!