Writing if/then Statements for Python Parser of ArcGIS Field Calculator

Question

For some reason I cannot get this code to work in the Field Calculator of ArcGIS Desktop 10.6.1. I'm trying to use the Python parser to populate the field "SHAP_CLAS" with multiple conditional statements based on "AREA_LA" and "AREA_PERI_SQR".

The code I've tried so far is:

def calc(AREA_LA, AREA_PERI_SQR):
   if (AREA_LA =< 100 and AREA_PERI_SQR =< 0.65):
       return 2
   elif (AREA_LA =< 100 and AREA_PERI_SQR > 0.65):
       return 1
   elif (100 < AREA_LA < 500 and AREA_PERI_SQR =< 0.45):
       return 2
   elif (100 < AREA_LA < 500 and AREA_PERI_SQR > 0.45):
       return 1
   else:
       return 3

...and...

calc(!SHAP_CLAS!)

...in the box below the code block.

PolyGeo · Accepted Answer · 2019-12-11 10:42:07Z

1

You've not told us what the error message you're receiving is, but from looking at your code I can see you're not using the correct operator for 'Less Than or Equal To'.

You've used:=< When it should be: <=

Correcting that should hopefully fix your issue.

edited Dec 11, 2019 at 10:42

PolyGeo♦

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answered Dec 11, 2019 at 8:53

Hyder Al Hassani

644 bronze badges

1

It will not work. Because she is calling a method with two attributes with only one provided (and the wrong one also). But you are right about the operator.

Jan Doležal
– Jan Doležal

2019-12-11 08:59:10 +00:00
Commented Dec 11, 2019 at 8:59
1

You are right about the operator. With @JanDoležal's code and '<=' it works, thank you!

Kimberly Clemons
– Kimberly Clemons

2019-12-11 10:42:13 +00:00
Commented Dec 11, 2019 at 10:42

Add a comment |

Jan Doležal · Accepted Answer · 2019-12-11 08:54:16Z

You were almost there, also call field calculator on the field you want to change ("SHAP_CLAS" for you):

def calc(AREA_LA, AREA_PERI_SQR): ##also change =< to <=
   if (AREA_LA =< 100 and AREA_PERI_SQR =< 0.65): 
       return 2
   elif (AREA_LA =< 100 and AREA_PERI_SQR > 0.65):
       return 1
   elif (100 < AREA_LA < 500 and AREA_PERI_SQR =< 0.45):
       return 2
   elif (100 < AREA_LA < 500 and AREA_PERI_SQR > 0.45):
       return 1
   else:
       return 3

and the change is here: (you are using method with 2 field, but then, you are providing only one field to the method)

calc(!AREA_LA!, !AREA_PERI_SQR!)

Basically the code is:

def method(field1, field2, fieldX):
    '''do something'''
    return value

and call:

method(!field1!,!field2!,!fieldX!)

There are some examples half way through at this page: http://desktop.arcgis.com/en/arcmap/10.3/manage-data/tables/calculate-field-examples.htm

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