Python, Matplotlib custom axes share Y axis

Question

I have simple code to create a figure with 7 axes/ custom subplots (my understanding is that subplots are equal-sized and equal-spaced and in my particular situation I need one to be larger than the rest).

fig = plt.figure(figsize = (16,12))
# row 1
ax1 = plt.axes([0.1,0.7,0.2,0.2])
ax2 = plt.axes([0.4,0.7,0.2,0.2])
ax3 = plt.axes([0.7,0.7,0.2,0.2])
# big row 2
ax4 = plt.axes([0.1, 0.4, 0.5, 0.2])
#row 3
ax5 = plt.axes([0.1,0.1,0.2,0.2])
ax6 = plt.axes([0.4,0.1,0.2,0.2])
ax7 = plt.axes([0.7,0.1,0.2,0.2])

my question is, how do i get all of these axes to share the same y-axis. All i can find on google/stack is for subplots, eg:

ax = plt.subplot(blah, sharey=True)

but calling the same thing for axes creation does not work:

ax = plt.axes([blah], sharey=True) # throws error

is there anyway to accomplish this? What I'm working with is:

Answer 1

This is quite simple using matplotlib.gridspec.GridSpec

gs=GridSpec(3,3) creates a 3x3 grid to place subplots on

For your top and bottom rows, we just need to index one cell on that 3x3 grid (e.g. gs[0,0] is on the top left).

For the middle row, you need to span two columns, so we use gs[1,0:2]

import matplotlib.pyplot as plt
from matplotlib.gridspec import GridSpec

fig=plt.figure(figsize=(16,12))

gs = GridSpec(3,3)

# Top row
ax1=fig.add_subplot(gs[0,0])
ax2=fig.add_subplot(gs[0,1],sharey=ax1)
ax3=fig.add_subplot(gs[0,2],sharey=ax1)

# Middle row
ax4=fig.add_subplot(gs[1,0:2],sharey=ax1)

# Bottom row
ax5=fig.add_subplot(gs[2,0],sharey=ax1)
ax6=fig.add_subplot(gs[2,1],sharey=ax1)
ax7=fig.add_subplot(gs[2,2],sharey=ax1)

ax1.set_ylim(-15,10)

plt.show()