Iterating field name in UpdateCursor?

Question

I have a series of fields to check for a certain value, then calculate other fields with using UpdateCursor.

Fields are: SPECIES_CD_1, SPECIES_CD_2, etc.. up to SPECIES_CD_99

Here is the general idea (some pseudocode in here):

rows = arcpy.UpdateCursor(FC) 
speciesLevel = "SPECIES_CD_"
for x in range (2,99):
    speciesX = speciesLevel + str(x) #this is a string
    speciesUnicode = speciesX.decode #Decodes the speciesX string to Unicode

    for row in rows:
    if row.speciesUnicode == 'P%':
        [do a whole bunch of things]
    elif row.speciesUnicode == None: 
        [do other things]
    else:
        [do other things]

Of course the cursor cannot identify a row named speciesUnicode, so the cursor fails to run. I want speciesUnicode to act as a variable that subs in a field name. Is this possible somehow?

Answer 1

You seem to be looking for values in all your SPECIES_CD_ fields that start with P. Here's a way to do this using list indices applied to your row. Note that I'm using the data access cursor so hopefully you're at 10.1 or above.

fc = ... #feature class
flds = ... #fields for cursor
with arcpy.da.UpdateCursor (fc, flds) as curs:
    for row in curs:
        for x in range (2, 99):
            fldName = "SPECIES_CD_" + str (x) #field name
            fldIndex = flds.index (fldName) #field index
            fldVal = row [fldIndex] #field value
            if type (fldVal) == str: ### check if value is a string
                if fldVal.startswith ("P"): #check if value starts with 'P'
                    [do a whole bunch of things]
            if fldVal == None:
                [do other things]
            else:
                [do other things]