Update cursor not working but with no errors [closed]

Question

I want my code to find the maximum value of a field from attribute table and return that as a the value for another field in another attribute table, trying to do this with search cursors and update cursor.

The search cursor seems to work fine, when I print the result is as expected, however, the update cursor does not return this value in the other attribute table but no errors are returned.

I am using ArcGIS Pro v. 3, arcpy with Python 3.

Here is my code:

fields = ["B1a_Score"]
all_rows = [i[0] for i in arcpy.da.SearchCursor(PA_Intersection,fields[0])]
max_val = max(all_rows)

print(max_val) #Correctly returns 4

AU = "AU_am"
field = ["B1a_Score"]

with arcpy.da.UpdateCursor(AU,field) as cursor:
    for row in cursor:
        row[0] = max_val
        cursor.updateRow(row) #B1a_Score in AU is not updated to 4 instead reads <null>

del cursor

Answer 1

It looks like your code is correct and it's not clear why the update cursor is not updating the values in the table as expected. There are a few things you can try to diagnose and solve the problem.

First, make sure that the field you are trying to update in the AU table exists and has the correct data type to hold the values you want to update it with. If the field does not exist or has the wrong data type, the update cursor will not be able to update it.

Next, try printing the values of the rows in the AU table before and after you update them using the update cursor. This will help you see if the values are actually being updated or not.

Finally, you can try using the arcpy.CalculateField_management() function instead of a search cursor and update cursor to see if it produces the same results. This function can be used to calculate the maximum value of a field in a table and update another field with that value in a single step.

Answer 2

The code originally sits within a function being called to calculate a field, I've changed to remove the update cursor and just return the max value, this seems to work for my overall purpose of calculating field:

    all_rows = [i[0] for i in arcpy.da.SearchCursor(PA_Intersection,fields[0])]
    max_val = max(all_rows)