Using Update Cursor within Search Cursor with ArcGIS Pro?

Question

I am new to using ArcPy/Python and I'm running into problems with a script I'm trying to write.

I'm using IDLE Python 3.6.8 ArcGIS Pro 2.4.0

Here is what I'm trying to do - I have 2 feature classes: 1. Water Mains, 2. Multi Ring buffer.

Within the Water Mains attribute table there is a "CriticalityScore" field. This is an integer value that is assigned based on the diameter(inches) of the pipe. Small diameter pipes = low value, larger diameter pipes receive higher values.

I am tasked with writing a script that will calculate this score for newly added pipes. I created a coded domain for a field called "Participation" to indicated "Yes/No". New pipes that are added into the attribute table by default receive "No."

What I have done so far is to assign if diameter = x then criticality score will = y.

Here's how the scores might look

1. 2" = (score of) 5
2. 4" = 9
3. 10" = 15 etc..

What I'm struggling with now is:

• Only updating "CriticalityScore" if "Participation" = "No"

Here's what I have so far

#set your workspace, where is this pulling data from? (gdb file path)  
  ws = env.workspace = r"H:\Python Scripts & Tools\Script Tester - Crit Scoring.gdb"

  #set the name of the shapefile path with which you're working (water main .shp)
  fclass = r"H:\Python Scripts & Tools\Script Tester - Crit Scoring.gdb\Water_Mains.shp"

  buffers = r"L:\Engineering\Brice\CriticalityScoringwPipeTestBrice.gdb\BufferParcelEmergancyResponceFac"

  #The third item in "fields" (index position [2])should be the Yes/No field in the feature class
  fields = ["Diameter", "CriticalityScore", "Participation"]


  with arcpy.da.UpdateCursor(fclass, fields) as cursor:
      while row[2] == No:
          for row in cursor:
            if row[0] == 2:
                row[1] = "5"
            elif row[0] == 3:
                row[1] = "7"
            elif row[0] == 4:
                row[1] = "9"
            elif row[0] == 6:
                row[1] = "11"
            elif row[0] == 8:
                row[1] = "13"
            elif row[0] == 10:
                row[1] = "15"
            elif row[0] == 12:
                row[1] = "17"
            elif row[0] == 16:
                row[1] = "20"
            else:
                row[1] = "22"
            cursor.updateRow(row)
          print("The script has finished.")

The script was working before I added the "While row[2] statement. As of right now it will run through the script and give me the ending print statement, but the .aprx/attribute table is never actually updated.

Answer 1

The first part of you question can be solved with a starting if statement. Or better use a where_clause in the cursor to only iterate over "No" rows. A while loop is not what you want as it will stop iterating when the first "Yes" is encountered.

And instead of multiple if-elif-else you can use a dictionary:

d = {2:"5", 3:"7", ..., 16:"20") #Add all your values.

with arcpy.da.UpdateCursor(fclass, fields) as cursor:
    for row in cursor:
        if row[2] == "No": #You forgot the quotes
            row[1] = d.setdefault([row[0], "22") #Fetch value. If not found use "22")
            cursor.updateRow(row)

For the second part you could try:

1. Add a field to the buffers with values of 20, 10 and 5
2. Intersect with points
3. Dissolve by point id and sum on value field
4. Join the results back to the original points
5. Include the joined field in your logic

Answer 2

This ended up working for me. Used both answers to help me finish. I removed the ".shp" from my file paths and that began to update the attribute table. I still don't understand the where clause so I think I'll have to read up on that and know how it works before I implement it.

  ws = env.workspace = r"H:\Python Scripts & Tools\Script Tester - Crit Scoring.gdb"
  #set the name of the shapefile path with which you're working (water main .shp)
  fclass = r"H:\Python Scripts & Tools\Script Tester - Crit Scoring.gdb\Water_Mains"
  #The third item in "fields" (index position [2])should be the Yes/No field in the feature class
  fields = ["Diameter", "CriticalityScore", "Participation"]
  d = {2:"5", 3:"7", 4:"9", 6:"11", 8:"13", 10:"15", 12:"17", 16:"20",}
  with arcpy.da.UpdateCursor(fclass, fields) as cursor:
    for row in cursor:
        if row[2] == "No": 
            if row[0] in d: #If row[0] is in dictionary keys
                row[1] = d[row[0]] #Fetch value
            else:
                row[1] = "22"
            cursor.updateRow(row)
    print("The script has finished.")```