Creating a Sierpinski triangle

Question

I'm attempting to create a Sierpinski triangle with the ezgraphics library using recursion. I imagine that there are several things that I have done wrong but I'm stuck as I am relatively new to coding. I'm not looking for someone to complete the code for me, just suggestions as to what to try next.

Here is the library I'm using: http://www.ezgraphics.org/ReferenceGuide/ReferenceGuide

And here is my rough code so far:

from ezgraphics import GraphicsWindow

def main():
    winSpec = int(input("enter the size of the window: "))
    subDiv = int(input("Enter number of subdivisions: "))
    win = GraphicsWindow(winSize,winSize)
    canvas = win.canvas()
    canvas.setColor( "blue" )
    triangle1 = [winSpec/2, 0, 0, winSpec, winSpec, winSpec]
    drawGasket(triangle1,subDiv,canvas)
    #canvas.drawPolygon(triangle1[0],triangle1[1],triangle1[2],triangle1[3],triangle1[4],triangle1[5])  
    win.wait()

def drawGasket(points,subDiv,canvas):    
    print(points)
    canvas.drawPolygon(points[0],points[1],points[2],points[3],points[4],points[5])  
    if subDiv > 0:
        print("hi")
        points2 = [points[0] + points[2] /2,points[1] + points[3] /2, points[0] + points[4] /2,points[1] + points[5] /2, points[2] + points[4] /2,points[3] + points[5] /2]
        drawGasket(points2, subDiv - 1, canvas)

Answer 1

You should draw only for subDiv == 0 and for other values you should calculate middle points and run again with three new triangles.

You have to use () to divide sum - (points[0] + points[2]) /2. Without () you divide second point before adding points.

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BTW

Shorter

 canvas.drawPolygon(points)

You can assing points to variables which means something to make code more readable

 x1, y1, x2, y2, x3, y3 = points

and then you can calculate middle points

 middle_1_2_x = (x1+x2)/2
 middle_1_2_y = (y1+y2)/2

 middle_2_3_x = (x2+x3)/2
 middle_2_3_y = (y2+y3)/2

 middle_1_3_x = (x1+x3)/2
 middle_1_3_y = (y1+y3)/2

before you create new triangles

 triangle1 = [x1, y1, middle_1_2_x, middle_1_2_y, middle_1_3_x, middle_1_3_y]
 triangle2 = [middle_1_2_x, middle_1_2_y, x2, y2, middle_2_3_x, middle_2_3_y]
 triangle3 = [middle_1_3_x, middle_1_3_y, middle_2_3_x, middle_2_3_y, x3, y3]

---

Result:

---

Full code:

from ezgraphics import GraphicsWindow

def main():
    #winSpec = int(input("enter the size of the window: "))
    #subDiv = int(input("Enter number of subdivisions: "))

    winSpec = 600
    subDiv = 2

    win = GraphicsWindow(winSpec, winSpec)
    canvas = win.canvas()
    canvas.setColor("blue")

    triangle = [winSpec/2, 0, 0, winSpec, winSpec, winSpec]
    print('start:', triangle)
    drawGasket(triangle, subDiv, canvas)

    win.wait()

def drawGasket(triangle, subDiv, canvas):    
    if subDiv == 0:
        print(' draw:', triangle)
        canvas.drawPolygon(triangle)
    else:
        x1, y1, x2, y2, x3, y3 = triangle

        middle_1_2_x = (x1+x2)/2
        middle_1_2_y = (y1+y2)/2
        print('middle 1-2:', middle_1_2_x, middle_1_2_y)

        middle_2_3_x = (x2+x3)/2
        middle_2_3_y = (y2+y3)/2
        print('middle 2-3:', middle_2_3_x, middle_2_3_y)

        middle_1_3_x = (x1+x3)/2
        middle_1_3_y = (y1+y3)/2
        print('middle 1-3:', middle_1_3_x, middle_1_3_y)

        triangle1 = [x1, y1, middle_1_2_x, middle_1_2_y, middle_1_3_x, middle_1_3_y]
        drawGasket(triangle1, subDiv-1, canvas)

        triangle2 = [middle_1_2_x, middle_1_2_y, x2, y2, middle_2_3_x, middle_2_3_y]
        drawGasket(triangle2, subDiv-1, canvas)

        triangle3 = [middle_1_3_x, middle_1_3_y, middle_2_3_x, middle_2_3_y, x3, y3]
        drawGasket(triangle3, subDiv-1, canvas)

main()