Basic Animation Technique in PyGame shown in my video: https://youtu.be/gUa1j7gY0yY

pygame_animate_spinning_line.py

import math
import pygame

# initial setups
pygame.init()
screen_size = 500
surface = pygame.display.set_mode((screen_size, screen_size)) # window size and pixels width/height

# animation state variables
angle_per_step = .05  # degrees
step = 0

# animation loop
while True:

    # erase background each time
    surface.fill((0, 0, 0))  # erase surface memory before we draw new things

    # calculate and draw rotating line
    angle = step * angle_per_step
    line_len = screen_size * .8
    cx = cy = screen_size // 2 # center of rotation
    x = line_len/2.0*math.sin(angle)
    y = line_len/2.0*math.cos(angle)
    pygame.draw.line(surface, (255,255,0), ((cx+x),(cy+y)),((cx-x),(cy-y)), 4)

    # update to display, await clock check for quit advance animation state
    pygame.display.update()
    pygame.time.Clock().tick(60)

    if pygame.event.peek(pygame.QUIT):  # detect user quit
        break

    step += 1  # advance state of animation


pygame.quit()  # close window