If field 1 > field 2 update field 3 in loop

Question

I am trying to update the table above. What I want to do is if the values in the PMP fields are less than the Max fields update the check fields with PASS, if not FAIL. I started doing this trying to create a list for the PMP fields and a list for the MAX fields and comparing them and updating a check list that I would use to populate the CHECK fields but had issues.

Could this be done using just an Update cursor or numpy somehow?

Here is what I had so far on my list attempt.

    pmpValues = []
    i = 0
    for pmpVal in pmpFields:
        with arcpy.da.SearchCursor(checkTable,pmpFields[i]) as cursor:
            for row in cursor:
                pmpValues.append([row])
        i += 1

    maxValues = []
    i = 0
    for maxVal in maxFields:
        with arcpy.da.SearchCursor(checkTable,maxFields[i]) as cursor:
            for row in cursor:
                maxValues.append([row])
        i += 1        

    checkValues = []
    for p in pmpValues:
        for m in maxValues:
            if p < m:
                check = "FAIL"
            else:
                check = "PASS"
            checkValues.append(check)

Answer 1

Here's how you could use an update cursor without having to worry about field order (untested):

# use a wildcard to return all fields for each row
with arcpy.da.UpdateCursor(fc, '*') as cursor:
    # grab the field names
    fields = cursor.fields
    # loop over rows
    for row in cursor:
        # create dict of field name -> field value
        rec = dict(zip(fields, row))
        # loop over dict keys and values
        for k, v in rec.iteritems():
            # act on PMP fields only
            if not k.startswith('PMP_'):
                continue
            # split the the numeric suffix from the PMP field name
            _, n = k.split('_')
            # lookup the max value for that given suffix
            mx = rec['MAX_{}'.format(n)]
            # set the CHECK value for that given suffix in our dict
            rec['CHECK_{}'.format(n)] = 'FAIL' if v < mx else 'PASS'
        # update values from the dict, ensuring that the order matches the row
        cursor.updateRow([rec[k] for k in fields])

Answer 2

You can use a modified version of the UpdateCursor code sample from http://desktop.arcgis.com/en/arcmap/10.3/analyze/arcpy-data-access/updatecursor-class.htm

With the update cursor, you pass your set of desired fields and can evaluate each row, then pass new values for each field/record.

import arcpy

fc = 'pathtofeatureclass'
fields = ['PMP_06', 'MAX_06', 'CHECK_06','PMP_12', 'MAX_12', 'CHECK_12','PMP_24', 'MAX_24', 'CHECK_24','PMP_48', 'MAX_48', 'CHECK_48']

# Create update cursor for feature class 
with arcpy.da.UpdateCursor(fc, fields) as cursor:
    # For each row, evaluate each PMP field value (index position 0,3,6,9)
    # vs MAX value (index position 1,4,7,10) 
    # and update CHECK (index position of 2,5,8,11)
    for row in cursor:
        if row[0] < row[1]:
            row[2] = 'PASS'
        else:
            row[2] = 'FAIL'
        if row[3] < row[4]:
            row[5] = 'PASS'
        else:
            row[5] = 'FAIL'
        if row[6] < row[7]:
            row[8] = 'PASS'
        else:
            row[8] = 'FAIL'  
        if row[9] < row[10]:
            row[11] = 'PASS'
        else:
            row[11] = 'FAIL'
        # Update the cursor with the updated list
        cursor.updateRow(row)