circle.py

import turtle

def circle(radius = 50, segments = 60):
    turn_step = 360 / segments
    segment_step = 6.28 * radius / segments
    
    turtle.left(turn_step / 2)
    for i in range(segments):
        color_step = 2 * i / (segments - 1)

        red = 2 - color_step
        if red > 1: red = 1
        
        blue = color_step
        if blue > 1: blue = 1
        
        turtle.pencolor(red, 0, blue)
        turtle.forward(segment_step)
        turtle.left(turn_step)
    turtle.right(turn_step / 2)

turtle.speed(0)
turtle.pensize(50)
circle(150)