In Matplotlib, How to avoid axvspan overlap?

Question

I noticed that two adjacent areas overlap, so in the middle appear an annoying line. I tried "capstyle = 'butt'" which I used to avoid overlap between lines, but here it doesn't do the job.

here's a minimal example:

import matplotlib.pylab as plt

ax = plt.subplot(111)

ax.axvspan(0, 0.5, color = 'red', alpha = 0.13, capstyle = 'butt')
ax.axvspan(0.5, 1, color = 'blue', alpha = 0.13, capstyle = 'butt')

plt.show()

Answer 1

The problem you have is not due to line caps, since axvspan draws a polygon. The problem is that this polygon, by default, has a border with a given linewidth (one pixel, I suppose).

So, to get just the areas without that "border", set the linewidth (lw) to zero:

import matplotlib.pylab as plt

ax = plt.subplot(111)

ax.axvspan(0, 0.5, color = 'red', alpha = 0.13, lw=0)
ax.axvspan(0.5, 1, color = 'blue', alpha = 0.13, lw=0)

plt.show()

Answer 2

Instead of color, use facecolor inside axvspan. The solution by @heltonbiker works great, it gets rid of the width of the border. But, at least in the matplotlib version I'm using, 2.0.0, using just facecolor doesn't draw the border.

import matplotlib.pylab as plt

fig,ax = plt.subplots()

ax.axvspan(0, 0.5, facecolor = 'red', alpha = 0.13)
ax.axvspan(0.5, 1, facecolor = 'blue', alpha = 0.13)

plt.show()

Using only facecolor will no draw the border:

Using color will fill the rectangle and will draw a border: