EX15.17.py

# 15.17 (Tkinter: Sierpinski triangle) Revise Listing 15.9 to let the user use leftmouse/
# right-mouse clicks to increase/decrease the current order by 1. The initial
# order is 0.

from tkinter import *  # Import tkinter


class SierpinskiTriangle:
    def __init__(self):
        window = Tk()  # Create a window
        window.title("Sierpinski Triangle")  # Set a title

        self.width = 200
        self.height = 200
        self.canvas = Canvas(window,
                             width=self.width, height=self.height)
        self.canvas.pack()

        # Add a label, an entry, and a button to frame1
        frame1 = Frame(window)  # Create and add a frame to window
        frame1.pack()

        self.order = 0
        self.display()

        self.canvas.bind("<Button-1>", self.increaseOrder)
        self.canvas.bind("<Button-3>", self.decreaseOrder)

        window.mainloop()  # Create an event loop

    def display(self):
        self.canvas.delete("line")
        p1 = [self.width / 2, 10]
        p2 = [10, self.height - 10]
        p3 = [self.width - 10, self.height - 10]
        self.displayTriangles(int(self.order), p1, p2, p3)

    def displayTriangles(self, order, p1, p2, p3):
        if order == 0:  # Base condition
            # Draw a triangle to connect three points
            self.drawLine(p1, p2)
            self.drawLine(p2, p3)
            self.drawLine(p3, p1)
        else:
            # Get the midpoint of each triangle's edge
            p12 = self.midpoint(p1, p2)
            p23 = self.midpoint(p2, p3)
            p31 = self.midpoint(p3, p1)

            # Recursively display three triangles
            self.displayTriangles(order - 1, p1, p12, p31)
            self.displayTriangles(order - 1, p12, p2, p23)
            self.displayTriangles(order - 1, p31, p23, p3)

    def drawLine(self, p1, p2):
        self.canvas.create_line(
            p1[0], p1[1], p2[0], p2[1], tags="line")

    # Return the midpoint between two points
    def midpoint(self, p1, p2):
        p = 2 * [0]
        p[0] = (p1[0] + p2[0]) / 2
        p[1] = (p1[1] + p2[1]) / 2
        return p

    def increaseOrder(self, event):
        self.order += 1
        self.display()

    def decreaseOrder(self, event):
        if self.order > 0:
            self.order -= 1
            self.display()


SierpinskiTriangle()  # Create GUI