Modification of matplotlib plt.subplots(), useful when some subplots are empty. It returns a grid where the plots in the last row are centered.

centered_subplots.py

import matplotlib.pyplot as plt
import matplotlib.gridspec as gridspec


def subplots_centered(nrows, ncols, figsize, nfigs):
    """
    Modification of matplotlib plt.subplots(),
    useful when some subplots are empty.
    
    It returns a grid where the plots
    in the **last** row are centered.
    
    Inputs
    ------
        nrows, ncols, figsize: same as plt.subplots()
        nfigs: real number of figures
    """
    assert nfigs < nrows * ncols, "No empty subplots, use normal plt.subplots() instead"
    
    fig = plt.figure(figsize=figsize)
    axs = []
    
    m = nfigs % ncols
    m = range(1, ncols+1)[-m]  # subdivision of columns
    gs = gridspec.GridSpec(nrows, m*ncols)

    for i in range(0, nfigs):
        row = i // ncols
        col = i % ncols

        if row == nrows-1: # center only last row
            off = int(m * (ncols - nfigs % ncols) / 2)
        else:
            off = 0

        ax = plt.subplot(gs[row, m*col + off : m*(col+1) + off])
        axs.append(ax)
        
    return fig, axs