Never mind, flowables have drawOn().
If I had only set up PythonWin's class browser *sooner*..
from common import *
from code39 import *
from code128 import *
from reportlab.pdfgen import canvas
def run():
    c = canvas.Canvas('barcodetest.pdf')
    c.drawString(50, 800, 'Code39')
    Standard39('Code39').drawOn(c,200,800)
    c.save()
if __name__=='__main__':
    run()