Remove gaps between subplots_mosaic in matplotlib

Question

How do I remove the gaps between the subplots on a mosaic? The traditional way does not work with mosaics:

plt.subplots_adjust(wspace=0, hspace=0)

I also tried using gridspec_kw, but no luck.

import matplotlib.pyplot as plt
import numpy as np

ax = plt.figure(layout="constrained").subplot_mosaic(
    """
    abcde
    fghiX
    jklXX
    mnXXX
    oXXXX
    """,
    empty_sentinel="X",
    gridspec_kw={
        "wspace": 0,
        "hspace": 0,
    },
)


for k,ax in ax.items():
    print(ax)
    #ax.text(0.5, 0.5, k, transform=ax.transAxes, ha="center", va="center", fontsize=8, color="darkgrey")
    ax.set_xticklabels([])
    ax.set_yticklabels([])
    ax.tick_params(length = 0)

The code generates:

Answer 1

This is not caused by subplot_mosaic but because a layout was specified. If you use constrained or tight layout, the layout manager will supersede the custom adjustments.

Remove the layout manager and either method will work:

• gridspec_kw

  fig = plt.figure() # without layout param
  ax = fig.subplot_mosaic(
      """
      abcde
      fghiX
      jklXX
      mnXXX
      oXXXX
      """,
      empty_sentinel="X",
      gridspec_kw={
          "wspace": 0,
          "hspace": 0,
      },
  )
  

• subplots_adjust

  fig = plt.figure() # without layout param
  ax = fig.subplot_mosaic(
      """
      abcde
      fghiX
      jklXX
      mnXXX
      oXXXX
      """,
      empty_sentinel="X",
  )
  fig.subplots_adjust(wspace=0, hspace=0)