Tkinter canvas rectangle appears with incorrect size depending on row/column – how to fix?

I am writing a Python tkinter rectangle function:

def Rectangle(row,col,color="#FFFFFF",outline="gray"):
    """
    Fills a block with a color.
    Args:
        row - The row 
        col - The column
        *color - The rectangle color
        *outline - The color of the outline
    """
    global blockwidth, blockheight, canvas
    x, y, i = blockCoords(row,col)
    canvas.create_rectangle(x//2,y//2,x*2,y*2,fill=color,outline=outline)

This function should make a rectangle at those (row, col) coordinates exactly one block (rectangle in the drawn grid, explained later) big.

def blockCoords(row, col):
    """
    Gets the row and col value of a digit.
    Args:
        rows - The block's row
        cols - The block's col
    Returns:
        The x and y coordinates and it's respective index
    """
    global blockwidth, blockheight, canwidth, canheight
    row -= 1
    col -= 1
    x = col * blockwidth + blockwidth // 2
    y = row * blockheight + blockheight // 2
    i = row+col
    return x, y, i

Then the rectangle function is called in the main function:

blockwidth = 20
blockheight = 40
win = tk.Tk()
states = []
win.title("Terminos App")
with open("set.json","r") as f:
    settings = json.load(f)

# create a canvas
canwidth = 1200
canheight = 800
canvas = tk.Canvas(win,width=canwidth,height=canheight,bg="#232627")
canvas.pack(fill=tk.BOTH,expand=tk.YES)

def main():
    """
    The main function that handles the window
    Args:
        event - A detected keypress
    """
    global win, canvas, canwidth, canheight, blockwidth, blockheight
    cols = canwidth//blockwidth
    rows = canheight//blockheight
    for row in range(canwidth):
        for col in range(canheight):
            states.append("")
            x1 = col * blockwidth
            y1 = row * blockheight
            x2 = x1 + blockwidth
            y2 = y1 + blockheight
            canvas.create_rectangle(x1, y1, x2, y2, outline="gray") # Used for debugging purposes
    Rectangle(10,15)

The code should create the rectangle I explained, but it creates one with a different size depending on the row and col coordinates. What is the problem and what is the solution? Thanks!

You're currently treating the center point (x, y) as if it were the top-left and bottom-right corners. Instead of x//2 and x*2, calculate the corners based on width and height like this:

canvas.create_rectangle(x - blockwidth // 2, y - blockheight // 2,
                        x + blockwidth // 2, y + blockheight // 2,
                        fill=color, outline=outline)

That way, the rectangle will be exactly blockwidth × blockheight in size, centred at the calculated coordinates.