Increase QPen Width

Question

I need to increase the pen width for the below code using Painter/QPen, but nothing that I try works. Can someone please point me in the right direction?

    while c_len < MAX_LENGTH:
        # Set the pen color for this segment
        sat = 200 * (MAX_LENGTH - c_len) / MAX_LENGTH
        hue = (color + 130 * (height - y_s) / height) % 360
        p.setPen(QPen(QColor_HSV(hue, sat, 255, 20), 2))