在matplotlib中使用tight_layout（）并使用不完整的轴数组：

Question

I am creating PDFs of an array of axes. Sometimes the page is not full, ie not all axes have data. In this case, I want the unused axes not to show on the PDF. But I want the layout to be the same as if they were being used. I'm using tight_layout() to get non-overlapping axes and ylabels.

The following code shows first the case where the axes are used, then what happens if I delete the unused ones (tight_layout does not work properly), and then, if I instead just set them not to be visible, tight_layout() fails with a

AttributeError: 'NoneType' object has no attribute 'is_bbox'

error.

import numpy as np
import matplotlib.pyplot as plt
def prep_figure():
    plt.close('all')
    fig, axs = plt.subplots(4,3, figsize=(11,8.5))
    axs=np.concatenate(axs)
    for ii in range(5):
        axs[ii].plot([1,2,3],[-10,-1,-10])
        axs[ii].set_ylabel('ylabel')
        axs[ii].set_xlabel('xlabel')
    return fig,axs

fig,axs=prep_figure()
plt.tight_layout()
plt.show()
plt.savefig('tmp.pdf', )

# Try deleting extra axes
fig,axs=prep_figure()
for ii in range(5,12):
    fig.delaxes(axs[ii])
plt.tight_layout()
plt.show()
plt.savefig('tmpd.pdf', )

# Try hiding  extra axes
fig,axs=prep_figure()
for ii in range(5,12):
    axs[ii].set_visible(False)
plt.tight_layout()
plt.show()
plt.savefig('tmph.pdf', )

I want the layout of the first version, but without the extra axes visible.

Answer 1

You could create the axes independently of the figure. I would also recommend this method because you have more control over the axes, for example you could have different shaped axes.

Code:

import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure()
for ii in range(5):
    ax = fig.add_subplot(4,3,ii+1)
    ax.scatter(np.random.random(5),np.random.random(5))
    ax.set_xlabel('xlabel')
    ax.set_ylabel('ylabel')
fig.tight_layout()
fig.show()

Result:

Answer 2

The second case of deleting the axes works fine if it is used on its own (without the code from the first case executed) and if the figure is first saved and then shown,

fig,axs=prep_figure()
for ii in range(5,12):
    fig.delaxes(axs[ii])
plt.tight_layout()
plt.savefig('tmpd.pdf', )
plt.show()

The third case works fine if again, the figure is saved before showing it, and instead of making it invisible, turning the axes off via ax.axis("off") .

fig,axs=prep_figure()
for ii in range(5,12):
    axs[ii].axis("off")
plt.tight_layout()
plt.savefig('tmph.pdf', )
plt.show()

The created pdf is the same in both cases: