VBA/Python If/then statements in Field Calculator for one column based on another not working

Question

I know this question has been asked a hundred times on here, for example:

• Basic If/Then in Python Parser of ArcGIS Field Calculator?
• Using if/elif/else statements in ArcGIS Field Calculator?
• Checking for values in one column and do something in another using ArcGIS Field Calculator?
• https://community.esri.com/thread/21689

but I just can't get my code to work. I am trying to do a simple if/then statement in field calculator. I have a column (risk_value) I want to populate based on the values in the other (risk_color). There are only four values in Risk_color: Green, yellow, red, null.

enter image description here

I tried writing code in VBA:

Pre-logic script Code:

Dim val
If [RISK_COLOR] = "Green" Then 
 val = "Low"
elseif [RISK_COLOR] = "Yellow" Then 
 val = "Medium"
elseif [RISK_COLOR] = "Red" Then 
 val = "High"
elseif [RISK_COLOR] = "<Null>" Then 
 val = "<Null>"
end if

---

RISK_VALUE=

val

enter image description here

Error executing function.

Then I tried python string:

def Value(color):
 if (color == 'Green'):
 return "Low"
 elif (color == 'Yellow'):
 return "Medium"
 elif (color == 'Red'):
 return "High"
 else:
 return "<Null>"

RISK_VALUE=Value(!RISK_COLOR!)

enter image description here

Error executing function.

What am I doing wrong?

• Bjorn: Double single quotes after Red in your Python code
• J.R: For the VBA code you should remove the Dim val at start. Also you have to check if your <null> value are really text (you seem to assume that in your code), if not they are null value and you should handle them differently
• ahmadhanb: @Bjorn I see it one single quote after 'Red'', but good catch.
• PolyGeo: If this question has been asked a hundred times before I think you should provide a link to at least one of those Q&As so that we can try to understand whether it needs to be improved/closed. We seek to only have useful Q&As on this site.

Answer 1

It is how you are dealing with Null values. You are treating Null as a string when it is NOTHING! How can nothing be something?

But now think about what you are asking, in your case if colour is not green, yellow or red then it can only be a Null value. So you don't need to test if it is Null as you have already checked all other options.

So your VB script code need only be:

Dim val
If [RISK_COLOR] = "Green" Then 
 val = "Low"
elseif [RISK_COLOR] = "Yellow" Then 
 val = "Medium"
elseif [RISK_COLOR] = "Red" Then 
 val = "High"
else 
 val = "<Null>"
end if