I was intrigued by a command line that I don’t understand, given in the answer of the (already old) post HERE.

So, I tried to investigate and made the following program:

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.lines import Line2D 
from scipy.spatial import Delaunay, delaunay_plot_2d

np.random.seed(12345)
points = np.random.rand(8, 2) 

tri = Delaunay(points)
fig, ax = plt.subplots(figsize=(8, 4))
D = delaunay_plot_2d(tri, ax=ax)
ax.set_aspect('equal', 'box')

list = [l for l in D.axes[0].get_children() if type(l) is Line2D]
list

which gave me 3 items in the list:

[<matplotlib.lines.Line2D at 0x246dd230550>,
 <matplotlib.lines.Line2D at 0x246dd230850>,
 <matplotlib.lines.Line2D at 0x246dd230af0>]

I then could use the 1st item to change the color of the points:

patch_point = [l for l in D.axes[0].get_children() if type(l) is Line2D][0] 
patch_point.set_color('blue')

and the 2nd item to change the color of the lines:

patch_line = [l for l in D.axes[0].get_children() if type(l) is Line2D][1] 
patch_line.set_color('green')    

but what is the meaning of the 3rd item? For example, the following lines doesn’t change anything…

patch_what = [l for l in D.axes[0].get_children() if type(l) is Line2D][2] 
patch_what.set_color('red')    

Could someone help me understanding what this strange command [l for l in D.axes[0].get_children() if type(l) is Line2D] does?