import matplotlib
matplotlib.use('WXAgg')
import matplotlib.pyplot as plt
import numpy as np
from datetime import datetime

def update_title(axes):
    axes.set_title(datetime.now())
    axes.figure.canvas.draw()
fig, ax = plt.subplots()
x = np.linspace(-3, 3)
ax.plot(x, x ** 2)
timer = fig.canvas.new_timer(interval=100)
timer.add_callback(update_title, ax)
timer.start()
plt.show()

Traceback (most recent call last):
  File "timer_debug.py", line 18, in <module>
    timer = fig.canvas.new_timer(interval=100)
  File "/Users/ewthornton/opt/anaconda3/envs/grid_gen3/lib/python3.7/site-packages/matplotlib/backend_bases.py", line 2374, in new_timer
    return self._timer_cls(interval=interval, callbacks=callbacks)
  File "/Users/ewthornton/opt/anaconda3/envs/grid_gen3/lib/python3.7/site-packages/matplotlib/backends/backend_wx.py", line 78, in __init__
    TimerBase.__init__(self, *args, **kwargs)
  File "/Users/ewthornton/opt/anaconda3/envs/grid_gen3/lib/python3.7/site-packages/matplotlib/backend_bases.py", line 1094, in __init__
    self.single_shot = False
  File "/Users/ewthornton/opt/anaconda3/envs/grid_gen3/lib/python3.7/site-packages/matplotlib/backend_bases.py", line 1145, in single_shot
    self._timer_set_single_shot()
  File "/Users/ewthornton/opt/anaconda3/envs/grid_gen3/lib/python3.7/site-packages/matplotlib/backends/backend_wx.py", line 91, in _timer_set_single_shot
    self._timer.Start()
wx._core.wxAssertionError: C++ assertion "m_milli > 0" failed at /opt/concourse/worker/volumes/live/3ef8f33f-8e5b-442f-6716-948fc4646a36/volume/wxpython_1547931203930/work/ext/wxWidgets/src/osx/core/timer.cpp(69) in Start(): invalid value for timer timeout