Algorithm to Pseudocode

 draggingToken = False
    tokenx, tokeny = None, None
    while True:
        for event in pygame.event.get():
            if event.type == QUIT:
                terminate()
            if not draggingToken and event.type == MOUSEBUTTONDOWN and redPileRect.collidepoint(event.pos):
                # start of dragging o`n red token pile.
                draggingToken = True
            if draggingToken and event.type == MOUSEMOTION:
                # draw red token being dragged
                tokenx, tokeny = event.pos
            if draggingToken and event.type == MOUSEBUTTONUP:
                # let go of dragging token.

                if tokeny < YMARGIN and tokenx > XMARGIN and tokenx < WINDOWWIDTH - XMARGIN:
                    # let go at the top of the screen.
                    column = int((tokenx - XMARGIN) / SPACESIZE)
                    if isValidMove(board, column):
                        animateDroppingToken(board, column, 'red')
                        board[column][getLowestFreeSpace(board, column)] = 'red'
                        drawBoard(board)
                        pygame.display.update()
                        return
                tokenx, tokeny = None, None
                draggingToken = False
        if tokenx != None and tokeny != None:
            drawBoard(board, {'x':tokenx - int(SPACESIZE / 2), 'y':tokeny - int(SPACESIZE / 2), 'color':'red'})
        else:
            drawBoard(board)

        pygame.display.update()
        gameClock.tick()