Matplotlib Line Rotation or Animation - python-3.x

Question

I have created a polar plot and would like to mimic a doppler. This includes a 360 degree sweep around the circle (polar plot). Once the sweep gets to 360 degrees, it needs to go back to zero and continue the sweep.
How do I animate or rotate this line to constantly sweep around this circle? I only want one line to constantly sweep around this plot.
I have looked at several different examples, however, none that create this rotation.
import numpy as np
import math
import matplotlib.pyplot as plt
import pylab
import time
r = 90 * (math.pi/180)
t = 50000
az = 90
el = 5
fig = pylab.figure(figsize = [5.0, 5.0])
ax = fig.gca(projection = 'polar')
fig.canvas.set_window_title('Doppler')
ax.plot(r, t, color ='b', marker = 'o', markersize = '3')
ax.set_theta_zero_location('N')
ax.set_theta_direction(-1)
currTime = time.time()
prevTime = currTime - 1
deltaTime = currTime - prevTime
outer_border_width = 1
screen_width = 500
screen_height = 500
midpoint = [int(screen_width/2), int(screen_height/2)]
radius = (midpoint[0])
sweep_length = radius - outer_border_width
angle = 50
sweep_interval = 10
sweep_speed = sweep_interval
x = sweep_length * math.sin(angle) + int(screen_width/2)
y = sweep_length * math.cos(angle) + int(screen_height/2)
az = az + ((360.0 / sweep_interval ) * deltaTime)
line1 = (midpoint, [50000, 50000])
#line2 = (midpoint, [20000, 20000])
ax.plot(line1, color = 'b', linewidth = 1)
#Increase the angle by 0.05 radians
angle = angle - sweep_speed
#Reset the angle to 0
if angle > 2 * math.pi:
angle = angle - 2 * math.pi
#ax.plot(line2, color = 'r', linewidth = 1)
#ax.lines.pop(0)
plt.show()
Below is a picture of what it currently looks like for reference:
Many thanks!

Answer 1

I do not understand much of your code, but in order to produce an animation you can use matplotlib.animation.FuncAnimation. Here, you'd give an array of angles to an updating function, which sets the data of the line for each frame.
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation
r = 90 * (np.pi/180)
t = 50000
fig = plt.figure()
ax = fig.gca(projection = 'polar')
fig.canvas.set_window_title('Doppler')
ax.plot(r, t, color ='b', marker = 'o', markersize = '3')
ax.set_theta_zero_location('N')
ax.set_theta_direction(-1)
ax.set_ylim(0,1.02*t)
line1, = ax.plot([0, 0],[0,t], color = 'b', linewidth = 1)
def update(angle):
line1.set_data([angle, angle],[0,t])
return line1,
frames = np.linspace(0,2*np.pi,120)
fig.canvas.draw()
ani = matplotlib.animation.FuncAnimation(fig, update, frames=frames, blit=True, interval=10)
plt.show()