Use UpdateCursor to update a field based on value in other field

Question

I'm trying to use a codeblock, that I've used in the field calculator of a shapefile before, in an ArcPy script with UpdateCursor.

The code I've used in the field calculator:

Pre-Logic Script Code:

def Reclass(NFK1M):
    if (NFK1M <= 50):
        return 10
    elif (NFK1M >50 and NFK1M <= 90):
        return 50
    elif (NFK1M > 90 and NFK1M <= 140):
        return 125
    elif (NFK1M> 140 and NFK1M <= 200):
        return 250
    elif (NFK1M > 200 and NFK1M <= 250):
        return 500
    elif (NFK1M > 250):
        return 750


Pktzl_B =
Reclass(!NFK1M!)

This works just fine. I've now tried to incorporate this in an arcpy-script with first creating the field "Pktz_B" and then filling it with UpdateCursor, but it always returns "750" from the last elif statement:

def punktzahl_b(fieldname):
    if 'NFK1M' <= 50:
        return 10
    elif 'NFK1M' > 50 and 'NFK1M' <= 90:
        return 50
    elif 'NFK1M' > 90 and 'NFK1M' <= 140:
        return 125
    elif 'NFK1M' > 140 and row1[0] <= 200:
        return 250
    elif 'NFK1M' > 200 and 'NFK1M' <= 250:
        return 500
    elif 'NFK1M' > 250:
        return 750


for fc in arcpy.ListFeatureClasses():
    if field_exists(fc, 'NFK1M'):
        arcpy.AddField_management(fc, 'Pktz_B', 'short')
        with arcpy.da.UpdateCursor(fc, 'Pktz_B') as cursor:
            for row in cursor:
                row[0] = punktzahl_b('NFK1M')
                cursor.updateRow(row)

I've also tried it like this, and it always returns "10" from the first if statement:

def punktzahl_b(fieldname):
    if row[0] <= 50:
        return 10
    elif row[0] > 50 and row[0] <= 90:
        return 50
    elif row[0] > 90 and row[0] <= 140:
        return 125
    elif row[0] > 140 and row[0] <= 200:
        return 250
    elif row[0] > 200 and row[0] <= 250:
        return 500
    elif row[0] > 250:
        return 750


for fc in arcpy.ListFeatureClasses():
    if field_exists(fc, 'NFK1M'):
        arcpy.AddField_management(fc, 'Pktz_B', 'short')
        with arcpy.da.UpdateCursor(fc, 'Pktz_B') as cursor:
            for row in cursor:
                row[0] = punktzahl_b('NFK1M')
                cursor.updateRow(row)

Answer 1

You need to include 'NFJK1M' field in the cursor and use it as input to the function:

...
for fc in arcpy.ListFeatureClasses():
    if field_exists(fc, 'NFK1M'):
        arcpy.AddField_management(fc, 'Pktz_B', 'short')
        with arcpy.da.UpdateCursor(fc, ['Pktz_B','NFK1M']) as cursor:
            for row in cursor:
                row[0] = punktzahl_b(row[1]) #here, row[1] is the NFK1M value
                cursor.updateRow(row)