cpython/Lib/turtledemo/sorting_animate.py

"""turtledemo/sorting_animation.py

A minimal sorting algorithm animation:
Sorts a shelf of 10 blocks using insertion
sort, selection sort and quicksort.

Shelves are implemented using builtin lists.

Blocks are turtles with shape "square", but
stretched to rectangles by shapesize()
"""
from turtle import *
import random


class Block(Turtle):

    def __init__(self, size):
        self.size = size
        Turtle.__init__(self, shape="square", visible=False)
        self.pu()
        self.shapesize(size * 1.5, 1.5, 2) # square-->rectangle
        self.fillcolor("black")
        self.st()

    def glow(self):
        self.fillcolor("red")

    def unglow(self):
        self.fillcolor("black")

    def __repr__(self):
        return "Block size: {0}".format(self.size)


class Shelf(list):

    def __init__(self, y):
        "create a shelf. y is y-position of first block"
        self.y = y
        self.x = -150

    def push(self, d):
        width, _, _ = d.shapesize()
        # align blocks by the bottom edge
        y_offset = width / 2 * 20
        d.sety(self.y + y_offset)
        d.setx(self.x + 34 * len(self))
        self.append(d)

    def _close_gap_from_i(self, i):
        for b in self[i:]:
            xpos, _ = b.pos()
            b.setx(xpos - 34)

    def _open_gap_from_i(self, i):
        for b in self[i:]:
            xpos, _ = b.pos()
            b.setx(xpos + 34)

    def pop(self, key):
        b = list.pop(self, key)
        b.glow()
        b.sety(200)
        self._close_gap_from_i(key)
        return b

    def insert(self, key, b):
        self._open_gap_from_i(key)
        list.insert(self, key, b)
        b.setx(self.x + 34 * key)
        width, _, _ = b.shapesize()
        # align blocks by the bottom edge
        y_offset = width / 2 * 20
        b.sety(self.y + y_offset)
        b.unglow()

def isort(shelf):
    length = len(shelf)
    for i in range(1, length):
        hole = i
        while hole > 0 and shelf[i].size < shelf[hole - 1].size:
            hole = hole - 1
        shelf.insert(hole, shelf.pop(i))
    return

def ssort(shelf):
    length = len(shelf)
    for j in range(0, length - 1):
        imin = j
        for i in range(j + 1, length):
            if shelf[i].size < shelf[imin].size:
                imin = i
        if imin != j:
            shelf.insert(j, shelf.pop(imin))

def partition(shelf, left, right, pivot_index):
    pivot = shelf[pivot_index]
    shelf.insert(right, shelf.pop(pivot_index))
    store_index = left
    for i in range(left, right): # range is non-inclusive of ending value
        if shelf[i].size < pivot.size:
            shelf.insert(store_index, shelf.pop(i))
            store_index = store_index + 1
    shelf.insert(store_index, shelf.pop(right)) # move pivot to correct position
    return store_index

def qsort(shelf, left, right):
    if left < right:
        pivot_index = left
        pivot_new_index = partition(shelf, left, right, pivot_index)
        qsort(shelf, left, pivot_new_index - 1)
        qsort(shelf, pivot_new_index + 1, right)

def randomize():
    disable_keys()
    clear()
    target = list(range(10))
    random.shuffle(target)
    for i, t in enumerate(target):
        for j in range(i, len(s)):
            if s[j].size == t + 1:
                s.insert(i, s.pop(j))
    show_text(instructions1)
    show_text(instructions2, line=1)
    enable_keys()

def show_text(text, line=0):
    line = 20 * line
    goto(0,-250 - line)
    write(text, align="center", font=("Courier", 16, "bold"))

def start_ssort():
    disable_keys()
    clear()
    show_text("Selection Sort")
    ssort(s)
    clear()
    show_text(instructions1)
    show_text(instructions2, line=1)
    enable_keys()

def start_isort():
    disable_keys()
    clear()
    show_text("Insertion Sort")
    isort(s)
    clear()
    show_text(instructions1)
    show_text(instructions2, line=1)
    enable_keys()

def start_qsort():
    disable_keys()
    clear()
    show_text("Quicksort")
    qsort(s, 0, len(s) - 1)
    clear()
    show_text(instructions1)
    show_text(instructions2, line=1)
    enable_keys()

def init_shelf():
    global s
    s = Shelf(-200)
    vals = (4, 2, 8, 9, 1, 5, 10, 3, 7, 6)
    for i in vals:
        s.push(Block(i))

def disable_keys():
    onkey(None, "s")
    onkey(None, "i")
    onkey(None, "q")
    onkey(None, "r")

def enable_keys():
    onkey(start_isort, "i")
    onkey(start_ssort, "s")
    onkey(start_qsort, "q")
    onkey(randomize, "r")
    onkey(bye, "space")

def main():
    getscreen().clearscreen()
    ht(); penup()
    init_shelf()
    show_text(instructions1)
    show_text(instructions2, line=1)
    enable_keys()
    listen()
    return "EVENTLOOP"

instructions1 = "press i for insertion sort, s for selection sort, q for quicksort"
instructions2 = "spacebar to quit, r to randomize"

if __name__=="__main__":
    msg = main()
    mainloop()