arcpy.CalculateField_management - compare: how to return fieldvalues

[SilvanStöckli]

Hello

I use a python script to compare the value of a field like follows:

def compare(class1):

   if class1 in (612, 611):
       return "Text1"
   elif class1 == 617:
       return "Text2"
   else:
       return !Field!‍‍‍‍‍‍‍‍

(followed by arcpy.CalculateField_management....)

this works perfectly to return a standardized text like "Text 1" or "Text 2".

But what I really want to do is I want to return a field-value instead of a text.

If (612, 611) return Field1-value;

if (617) return Field2-value.

I tried it with !Field! instead of "Text 1" but it didn't work.

What's the code to return a fieldvalue instead of text?

Thanks for your help!

[DanPatterson_Retired]

You would have to change !Field1! to class1 since class1 is representing what you find in Field1 and your script as it stands, has no idea what Field1 is.  

[SilvanStöckli]

thanks for your help

the problem ist that I don't want to return the value from the field I'm comparing with but the value from an other field in the same table.

That's why I tried to use !"AnotherFieldName"! with those "!!"

[DanPatterson_Retired · Accepted solution]

def compare(class1, another_value):

   if class1 in (612, 611):
       return "Text1"
   elif class1 == 617:
       return "Text2"
   else:
       return another_value

# Expression below

compare(!some_field!, !another_field!)‍‍‍‍‍‍‍‍‍‍‍‍

[SilvanStöckli]

I thought I found the solution:

return arcpy.CalculateField_management(fc, field, "!AnotherFieldName!", "PYTHON_9.3", "")‍‍

But this calculates new values for the whole table instead of only for the ones with value 612 in "field"

Any idea?

Thanks for your help!

[JoshuaBixby]

Calculate Field is a set-based tool.  If you want to update only a subset of records, you need to either create a feature layer and apply a selection set or embed some logic into the code block.

[LukeWebb]

Dan posted the solution, ill rewrite it more explicitly for your question.  You can pass as many values/fields to a function as you like so that you can then return their values.

def compare(class1, class2, class3):

   if class1 in (612, 611):
       return class2
   elif class1 == 617:
       return class3
   else:
       return class1

# Expression below

compare(!some_field!, !another_field!, !another_field2!)