Sharing a yaxis label with two of three subplots in pyplot

Question

I have the following code which produces the plot shown.

mport matplotlib.pyplot as plt 
import matplotlib.gridspec as gridspec
import numpy as np

One = range(1,10)
Two = range(5, 14) 
l = len(One)
fig = plt.figure(figsize=(10,6))
gs = gridspec.GridSpec(3, 1, height_ratios=[5, 3, 3]) 

ax0 = plt.subplot(gs[0])
ax0.bar(range(l), Two)
plt.ylabel("Number of occurrence")

ax1 = plt.subplot(gs[1], sharey=ax0)
ax1.bar(range(l), Two)

ax2 =  plt.subplot(gs[2])
ax2.bar(range(l), One)

plt.show()

I want the ylabel (" Number of occurrence") to be shared between first and second plot, that is, it should occur in the center left of first and second plot. How do I do that?

Answer 1

The best way I can think of is to add the text to the figure itself and position it at the center (figure coordinates of 0.5) like so

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

One = range(1,10)
Two = range(5, 14)
l = len(One)
fig = plt.figure(figsize=(10,6))
gs = gridspec.GridSpec(3, 1, height_ratios=[5, 3, 3])

ax0 = plt.subplot(gs[0])
ax0.bar(range(l), Two)

ax1 = plt.subplot(gs[1], sharey=ax0)
ax1.bar(range(l), Two)

ax2 =  plt.subplot(gs[2])
ax2.bar(range(l), One)

fig.text(0.075, 0.5, "Number of occurrence", rotation="vertical", va="center")

plt.show()

Answer 2

You can also adjust the position manually, using the y parameter of ylabel:

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

One = range(1,10)
Two = range(5, 14) 
l = len(One)
fig = plt.figure(figsize=(10,6))
gs = gridspec.GridSpec(3, 1, height_ratios=[5, 3, 3]) 

ax0 = plt.subplot(gs[0])
ax0.bar(range(l), Two)
plt.ylabel("Number of occurrence", y=-0.8)          ##  ← ← ← HERE

ax1 = plt.subplot(gs[1], sharey=ax0)
ax1.bar(range(l), Two)

ax2 =  plt.subplot(gs[2])
ax2.bar(range(l), One)

plt.show()