How to use Arcpy UpdateCursor to update a field?

Question

This should be simple but I've spent days trying everything to get it to work. I need to update a field in a layer based on two other fields. I can't even get it to update based on one field. Could someone please tell me whats wrong. So in this script I want to be classifying the outfield as "poor" if the infield is "Sandy". I will also have another field of numbers (and infield2 = "10").

rows = arcpy.UpdateCursor(infc) #this is my feature layer
for row in rows:
    if row.getValue(Infield1) == "Sandy":
        row.setValue(Outfield, "poor")
    else:
        row.setValue(Outfield, "none")
    rows.updateRow(row)
del rows

Thanks for all the answers. The script only works if written like this: I did not want to name the field names though, but at least it works.

The only way I could do a range 5 - 10 was to put > 5 and <10 (see line 23)

for row in rows:
    if row.getValue("Texture") == "Sandy" and row.getValue("Humus") < 10:
        row.setValue("Richness", "poor")
    elif row.getValue("Texture") == "Sandy" and row.getValue("Humus") > 10:
        row.setValue("Richness", "medium")
    elif row.getValue("Texture") == "Sandy-Clay" and row.getValue("Humus") < 5:
        row.setValue("Richness", "poor")
    elif row.getValue("Texture") == "Sandy-Clay" and row.getValue("Humus")  >= 5 and row.getValue("Humus")  <= 10:
        row.setValue("Richness", "medium")
    elif row.getValue("Texture") == "Sandy-Clay" and row.getValue("Humus") > 10:
        row.setValue("Richness", "rich")
    elif row.getValue("Texture") == "Clay" and row.getValue("Humus") < 5:
        row.setValue("Richness", "poor")
    elif row.getValue("Texture") == "Clay" and row.getValue("Humus") > 5:
        row.setValue("Richness", "rich")
    else:
        row.setValue("Richness", "unclassified")
    rows.updateRow(row)
del rows, row

Answer 1

Try removing the parentheses from your "if" statements so that you have:

if row.getValue("Infield1") == "Sandy":

Answer 2

    cur = arcpy.UpdateCursor(infc, "Where Infield1 = 'Sandy'") #this is my feature layer
    for row in cur:
        row.Outfield = "poor"
        cur.updateRow(row)
        del row
    del cur

    cur = arcpy.UpdateCursor(infc, "Where Infield1 <> 'poor'") #this is my feature layer
    for row in cur:
        row.Outfield = "none"
        cur.updateRow(row)
        del row
    del cur

or

cur = arcpy.UpdateCursor(infc) 
for row in cur:
    if row.Infield1 == "Sandy":         
        row.Outfield = "poor"    
    else:         
        row.Outfield = "none"    
    cur.updateRow(row) 
    del row
del cur

Is how I would do this. Too many times I have had issues trying to retrieve values with getValue(fieldname) so I reference the columns themselves as row.columnName and it works fine

Hope this helps.

Answer 3

Change

del rows

to

del rows, row