matplotlib: polar plots with a 'notch'

Question

is there a way i can decorate my polar/radial plots with 'notches' at locations r=0 or r=outer_edge? below is an example. By 'notches' i mean the red and blue lines at the origin and at the edge of the plot.

The code below can be used to generate a polar plot.

import numpy as np
import matplotlib.pyplot as plt

data = [-121,87,118,87,109,-139,-112,115,153,-109,-106,-92,75,-98,103,-89,
    152,114,77,-109,77,107,-77,106,-158,-71,-166,97,144,-166,138,39,130,
    -71,-76,-82,128,74,-47,94,-119,130,76,-86,-85,108,-78,-96,-113,82,
    127,-168,72,83,-61,-99,-83,-130,-69,43]

r = np.arange(0, len(data))
ax = plt.subplot(111,polar=True)
ax.scatter(data,r)
plt.show()

Answer 1

You could use annotate:

plt.annotate(' ',xy=(0, 0),  # theta, radius
            xytext = (-np.pi/10,len(data)/6.),
            textcoords='data',
            arrowprops=dict(facecolor='red', shrink=0.05))
plt.annotate(' ',xy=(np.pi/4.2, 1.355*max(r)),  # theta, radius
            xytext = (np.pi/4.2, 1.2*max(r)),
            textcoords='data',
            arrowprops=dict(facecolor='blue', shrink=0.05))

Or you can use plot:

rmax = ax.get_rmax()
theta_startstop = [2*[-np.pi/10],2*[np.pi/4.2]]
r_startstop = [[0,0.1*rmax],[0.9*rmax,rmax]]
notchcolor = ['red', 'blue']
for i in range(len(r_startstop)):
    ax.plot(np.array(theta_startstop[i]), np.array(r_startstop[i]),
            lw=3, c=notchcolor[i])
ax.set_rmax(rmax)

The result will be: