how can i make my figure made by matplotlib response to a mouse click event? - matplotlib

Question

I read the document of matplotlib and write the following code, it supposed to capture my mouse event and move the grey line position when i clicked. I read this code in jupiter notebook online, it stop to show the coordinate of my cursor as it usually do, What's happend? Can anyone help me?
import pandas as pd
import numpy as np
import matplotlib.colors as mcol
import matplotlib.cm as cm
from scipy import stats
from matplotlib.lines import Line2D
import matplotlib.pyplot as plt
import scipy.spatial as spatial
np.random.seed(12345)
df = pd.DataFrame([np.random.normal(33500,150000,3650),
np.random.normal(41000,90000,3650),
np.random.normal(41000,120000,3650),
np.random.normal(48000,55000,3650)],
index=[1992,1993,1994,1995])
fig, ax = plt.subplots()
year_avg = df.mean(axis = 1)
year_std = df.std(axis = 1)
yerr = year_std / np.sqrt(df.shape[1]) * stats.t.ppf(1-0.05/2, df.shape[1]-1)
bars=ax.bar(range(df.shape[0]), year_avg, yerr = yerr, color = 'lightslategrey')
threshold=42000
line=plt.axhline(y = threshold, color = 'grey', alpha = 0.5)
cm1 = mcol.LinearSegmentedColormap.from_list("CmapName",["yellow", "orange", "red"])
cpick = cm.ScalarMappable(cmap=cm1)
percentages = []
cpick.set_array([])
def setColor(bars, yerr,threshold):
for bar, yerr_ in zip(bars, yerr):
low = bar.get_height() - yerr_
high = bar.get_height() + yerr_
percentage = (high-threshold)/(high-low)
if percentage>1: percentage = 1
if percentage<0: percentage=0
percentages.append(percentage)
cpick.to_rgba(percentages)
bars = ax.bar(range(df.shape[0]), year_avg, yerr = yerr, color = cpick.to_rgba(percentages))
return bars
line=plt.axhline(threshold, color = 'grey', alpha = 0.5)
setColor(bars, yerr,threshold)
plt.colorbar(cpick, orientation='horizontal')
plt.xticks(range(df.shape[0]), df.index)
fig = plt.figure()
plt.show()
def onclick(event):
print('%s click: button=%d, x=%d, y=%d, xdata=%f, ydata=%f' %
('double' if event.dblclick else 'single', event.button,
event.x, event.y, event.xdata, event.ydata))
line.set_ydata(event.ydata)
#plt.draw()
cid = fig.canvas.mpl_connect('button_press_event', onclick)