I created a simple 'Code Block' python script for the Field Calculator in ArcGIS 10. It was working fine then. Since I installed ArcGIS 10.1, something strange is happening when I run it. The purpose is to concatenate 3 different text fields into a new field as Provincial Code (2 numbers) + Trail Code (4 numbers) + Section Code (1 letter). Provincial Code and Trail codes don't have Null values but the Section code has Null value in it. So when a section code exist, the Project Code will look like 01-0001A but with look like 01-0001 if no section code exists. Here is the 'Code Block' I'm using:
So when the Section code is Null or empty, I want to concatenate provincial and trail only (don't want any space or anything else after). Then, if a section code exist, I want to concatenate all of them together. As I said, it was working fine in ArcGIS 10. With ArcGIS 10.1, the code seems to only calculate the 'else' statement. If a section code exist, the code returns as expected something like 01-0001A. However, if section code is Null, instead of having something like 01-0001 I have 01-0001None. I don't understand why None appears now at the end.
Modify your codeblock slightly. Instead of testing a certain value ("") for section, use the generic statement whether section has some value. Your code should look like this:
def classify(prov, trail, section):
if section: # if section has any value
return prov + "-" + trail + section
else: # if section is empty or null or None
return prov + "-" + trail
Modify your codeblock slightly. Instead of testing a certain value ("") for section, use the generic statement whether section has some value. Your code should look like this:
def classify(prov, trail, section):
if section: # if section has any value
return prov + "-" + trail + section
else: # if section is empty or null or None
return prov + "-" + trail
Thanks Ahmed for your quick reply. However, I'm still facing the same issue...None appears at the end each time I have Null value as section code.
Thank you very much Jason. I don't really understand why I need to do this, but it's working now. I read somewhere that for Null values we had to put str in the expression and not in the code block. Can you explain the logic behind this?
Null values used to behave somewhat inconsistently; now they are correctly treated as the python value None across the system. You can do something like
if value is None
now in places to test if a value is Null in the table.
