How to set zero margins of the figure - matplotlib - python-3.x

Question

How to crop the figure to have no white space where nothing is plotted? Why plt.tight_layout(pad=0) does not work? The picture draw 3d coordinate system.
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
import numpy as np
fig = plt.figure(figsize=[5,3])
ax = fig.gca(projection = '3d')
ax.set_ylim(-2,3)
ax.set_zlim(-1,2)
vleng = 5
aleng = vleng/3.
p = np.array([vleng+200, 0, 0])
q = np.array([0, vleng-2, 0])
r = np.array([0, 0, vleng-3])
ax.plot(*np.vstack([[0,0,0], p]).T, color='black')
ax.plot(*np.vstack([[0,0,0], q]).T, color='black')
ax.plot(*np.vstack([[0,0,0], r]).T, color='black')
ax.azim = 20 # y rotation (default=270)
ax.elev = 20 # x rotation (default=0)
ax.dist = 10 # zoom (define perspective)
ax.set_axis_off( ) # hide all grid
plt.tight_layout(pad=0)
plt.show()
The output:
figure

Answer 1

So I tried multiple things. The only thing that would reduce these white spaces would require the three lines to be drawn along the meeting lines of the planes. So I did some measurements and here's the code where the white spaces have significantly reduced. You're free to reduce it further by tweaking it some more. Also comment out ax.set_axis_off( ) to see what's happening:
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
import numpy as np
fig = plt.figure(figsize=[5,3])
ax = fig.gca(projection = '3d')
ax.set_ylim(0,3)
ax.set_zlim(0,2)
# ax.set_xlim(0,2)
vleng = 5
aleng = vleng/3.
p = np.array([vleng+200, 0, 0])
q = np.array([0, vleng-2, 0])
r = np.array([0, 0, vleng-3])
ax.plot(*np.vstack([[0,0,0], p]).T, color='black')
ax.plot(*np.vstack([[0,0,0], q]).T, color='black')
ax.plot(*np.vstack([[0,0,0], r]).T, color='black')
ax.azim = 20 # y rotation (default=270)
ax.elev = 20 # x rotation (default=0)
ax.dist = 10 # zoom (define perspective)
ax.set_axis_off( ) # hide all grid
plt.tight_layout(pad=0)
plt.show()