Bug report

Bug summary

Might be a documentation issue. The constrainedlayout_guide says

constrained_layout needs to be activated before any axes are added to a figure. Two ways of doing so are

• using the respective argument to subplots() or figure(),
• [...]

However, fig = plt.figure(constrained_layout=True) does not seem to have any effect.

Code for reproduction

import matplotlib.pyplot as plt

def example_plot(ax, fontsize=12):
    ax.plot([1, 2])
    ax.set_xlabel('x-label', fontsize=fontsize)
    ax.set_ylabel('y-label', fontsize=fontsize)
    ax.set_title('Title', fontsize=fontsize)

fig = plt.figure(constrained_layout=True)
ax1 = fig.add_subplot(211)
ax2 = fig.add_subplot(212)

for ax in [ax1, ax2]:
    example_plot(ax, fontsize=24)
plt.show()

Actual outcome

Expected outcome

Matplotlib version

• Operating system: Windows 8.1
• Matplotlib version: 3.1.0
• Matplotlib backend (print(matplotlib.get_backend())): Qt5Agg
• Python version: 3.7