recursive function to walk up flow table. NOTE: this will not handle braided flowlines!

walk_up.py

from StreamCat_functions import dbf2DF

pre = 'D:/NHDPlusV21/NHDPlusGL/NHDPlus04'
fline = dbf2DF('D%s/NHDSnapshot/Hydrography/NHDFlowline.dbf' % pre)
flow = dbf2DF('%s/NHDPlusAttributes/PlusFlow.dbf' pre)[['TOCOMID','FROMCOMID']]

def recurs(val, ups):
    print val
    ups = ups + flow.ix[flow.TOCOMID == val].FROMCOMID.tolist()
    if 0 in ups:
        ups.remove(0)
    # here is where you would calculate whatever value that you want to pass through
    area = fline.ix[fline.COMID == val].LENGTHKM.values[0]
    # in this case I just grabbed length of the flowline
    if ups:
        return area + recurs(ups.pop(), ups)
    else:
        return area
      
recurs(4796914,[])