Python & Turtle

circle.py

import turtle

#by changing the value of step, the resulting graphic changes
#the larger step is, the less accurate the curve is (and the faster the circle is rendered)
step = 10
#to have a full circle path, divide 360 by the step value. int() assures the result is an integer
rg = int(360 / step)

for i in range(rg):
    turtle.forward(step)
    turtle.left(step)
    #if you print(i) you will see the number of steps that were needed to make the circle
    #print(i) 

turtle.exitonclick()

graphical result (used 60, 50, 10, 1, 0.5 and 0.1 as step)

circle_function.py

import turtle

#turtle.circle(radius, extent=None, steps=None)

for i in range(0, 180, 30):
    turtle.circle(i)

turtle.exitonclick()

graphical result

circle_function_centric.py same as previous function, but reseting the turtle position so that the circles have the same center

import turtle

for i in range(0, 180, 30):    
    turtle.pd()
    turtle.circle(i)
    turtle.pu()
    turtle.goto(0,-i)

turtle.exitonclick()

graphical result

centric_expansion.py

import turtle

for i in range(360):
    turtle.forward(i)
    turtle.left(i)

graphical result