I’ve stumbled upon a weird problem - matplotlib animation in my Python script works fine on Windows and Linux, but doesn’t show up on Mac OS. Here’s a video demonstration.

## The script source code

```
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
import math
# define x coordinates
x0, x1 = 0, 1
n = 500
x = np.linspace(x0, x1, n)
dx = x[1] - x[0]
# define time coordinates
t0, t1 = 0, 1
m = 500
t = np.linspace(t0, t1, m)
dt = t[1] - t[0]
# define velocity
uleft, uright = 1.0, 1.0
c = np.linspace(uleft, uright, x.shape[0])
# calculate stability
stab = np.amax(c) * dt / dx
print(f"stability r: {stab}")
# position in x
xs = 0.5
# width of the wavelet
rick = 0.1
xxsq = np.square((x - xs) / rick)
r = (1 - 12 * np.pi * xxsq) * np.exp(-6 * np.pi * xxsq)
# define two subplots
fig, ax = plt.subplots(2)
# plot ricker wavelet
ax[0].plot(x,r)
ax[0].set(
xlabel="x",
ylabel="displacement",
title="initial displacement, Ricker wavelet",
ylim=[-1.0, 1.0]
)
# initial displacement
u0 = r
# make sure boundary conditions are fulfilled
u0[0], u0[-1] = 0, 0
# initial velocity
ut0 = np.zeros(n)
# estimate second space derivative at t = 0
uxx0 = np.concatenate((u0, np.zeros(2))) \
- 2 * np.concatenate((np.zeros(1), u0, np.zeros(1))) \
+ np.concatenate((np.zeros(2), u0))
# estimate the first time step
u1 = u0 + dt * ut0 + dt * dt / 2 / dx / dx * c * c * uxx0[1:-1]
# initialize u with zeros
u = np.zeros(n)
# define matrix to make all spatial derivatives at once
A = np.diag(2 * np.ones(n - 2)) \
+ np.diag(-np.ones(n - 3), -1) \
+ np.diag(-np.ones(n - 3), 1)
A = dt * dt / dx / dx * A
# the free inner points where no boundary conditions are prescribed
free = np.linspace(1, n - 2, n - 2, dtype="int")
# velocity squared
c2 = c * c
c2 = c2[free]
# time loop
tmp0 = u0[free] # first time step
tmp1 = u1[free] # second time step
#prepare the subplot for the displacement
ax[1].set(
ylim=(-1.0, 1.0),
xlabel="x",
ylabel="displacement",
title="explicit fd solution of 1d wave eqn"
)
def animate(it):
global tmp0, tmp1
# predict u in the next time step
u[free] = 2 * tmp1 - tmp0 - c2 * np.dot(A, tmp1)
# update the previous time steps
tmp0 = tmp1
tmp1 = u[free]
line, = ax[1].plot(x, u)
return line,
# total time of animation in ms
totaltime = 1000
tint = totaltime / m
ani = animation.FuncAnimation(
fig,
animate,
np.arange(m),
interval=tint,
blit=True,
repeat=False
)
plt.show()
```

On all 3 systems (Windows, Linux, Mac OS) I only installed **matplotlib** and **numpy**, so the environment is seemingly the same.

## Environments

```
# Windows (10.19041.450, x64)
- Python 3.7.2
- matplotlib 3.3.1
- numpy 1.19.1
# Linux (Ubuntu 20.04.1, x64)
- Python 3.8.2
- matplotlib 3.3.1
- numpy 1.19.1
# Mac OS (10.15.6, x64)
- Python 3.8.5
- matplotlib 3.3.1
- numpy 1.19.1
```

I’ve tried some animation examples from documentation, and they work fine on Mac OS, so it should be something about my particular script.

Do have any guess what could be different in my case and how to make my animation work on Mac OS too?

I’ve also posted this question on Stack Overflow.