tree_fractal.py

# draws a tree
import turtle

# set the canvas window


def set_canvas():
    s = turtle.Screen()
    s.setup(450, 410)
    s.bgcolor('ivory')
    s.title('Turtle Program')
    return s

# set a turtle (a pen)


def set_pen(color):
    t = turtle.Turtle()
    t.shape('turtle')
    t.pen(pencolor=color, fillcolor=color, pensize=1, speed=10)
    return t


# draw a tree fractal using recursion
def draw_tree(t, branch, angle, n):
    if n <= 0:  # base case
        return
    else:  # recursive step
        t.forward(branch)
        t.right(angle)
        draw_tree(t, branch * 0.75, angle, n - 1)  # right branch
        t.left(angle * 2)
        draw_tree(t, branch * 0.75, angle, n - 1)  # left branch
        t.right(angle)
        t.backward(branch)


# main program
if __name__ == '__main__':
    s = set_canvas()
    t = set_pen('brown')
    t.penup()
    t.goto(-45, -150)
    t.left(90)
    t.pendown()
    draw_tree(t, 60, 20, 6)