Python's matplotlib legend in separate axis with gridspec

Question

Let suppose I have a matplotlib's gridspec instance in a python script. What I want to do is to create two axis and have the plot in one axis and the legend in the other one. Something like

import numpy as np
from matplotlib import gridspec, pyplot as plt

x = np.linspace(0,100)
y = np.sin(x)

gs = gridspec.GridSpec( 100, 100 )
ax1 = fig.add_subplot(gs[ :50, : ])
ax2 = fig.add_subplot(gs[ 55:, : ])
ax1.plot( s, y, label=r'sine' )
ax2.legend() # ?? Here I want legend of ax1
plt.show()

Is there any way of doing that?

Answer 1

You can grab the legend handles and labels from the first subplot using ax1.get_legend_handles_labels(), and then use them when you create the legend on the second subplot.

From the docs:

get_legend_handles_labels(legend_handler_map=None)

Return handles and labels for legend

ax.legend() is equivalent to:

h, l = ax.get_legend_handles_labels() 
ax.legend(h, l)

import numpy as np
from matplotlib import gridspec, pyplot as plt

x = np.linspace(0, 100)
y = np.sin(x)

fig = plt.figure()

gs = gridspec.GridSpec(100, 100 )
ax1 = fig.add_subplot(gs[:50, :])
ax2 = fig.add_subplot(gs[55:, :])

ax1.plot(x, y, label=r'sine')

h, l = ax1.get_legend_handles_labels() # get labels and handles from ax1

ax2.legend(h, l)                       # use them to make legend on ax2

plt.show()