pie.py

"""This module contains code from
Think Python by Allen B. Downey
http://thinkpython.com

Copyright 2012 Allen B. Downey
License: GNU GPLv3 http://www.gnu.org/licenses/gpl.html

"""

import math

try:
    # see if Swampy is installed as a package
    from swampy.TurtleWorld import *
except ImportError:
    # otherwise see if the modules are on the PYTHONPATH
    from TurtleWorld import *


def draw_pie(t, n, r):
    """Draws a pie, then moves into position to the right.

    t: Turtle
    n: number of segments
    r: length of the radial spokes
    """
    polypie(t, n, r)
    pu(t)
    fd(t, r*2 + 10)
    pd(t)

    
def polypie(t, n, r):
    """Draws a pie divided into radial segments.

    t: Turtle
    n: number of segments
    r: length of the radial spokes
    """
    angle = 360.0 / n
    for i in range(n):
        isosceles(t, r, angle/2)
        lt(t, angle)


def isosceles(t, r, angle):
    """Draws an icosceles triangle.

    The turtle starts and ends at the peak, facing the middle of the base.

    t: Turtle
    r: length of the equal legs
    angle: peak angle in degrees
    """
    y = r * math.sin(angle * math.pi / 180)

    rt(t, angle)
    fd(t, r)
    lt(t, 90+angle)
    fd(t, 2*y)
    lt(t, 90+angle)
    fd(t, r)
    lt(t, 180-angle)


# create the world and bob
world = TurtleWorld()
bob = Turtle()
bob.delay = 0
pu(bob)
bk(bob, 130)
pd(bob)

# draw polypies with various number of sides
size = 40
draw_pie(bob, 5, size)
draw_pie(bob, 6, size)
draw_pie(bob, 7, size)
draw_pie(bob, 8, size)
die(bob)

# dump the contents of the campus to the file canvas.eps
world.canvas.dump()

wait_for_user()