Python IF/THEN within Field Calculator

CoyPotts1

Hello,

I am trying to create a python IF/THEN statement within a model that runs the field calculator tool.  Essentially I want it to check to make sure if a cell has data entered (IS NOT NULL), and if so, calculate a concatenation of 4 other fields. 

Sample of what I want:

IF field1 <> NULL

    THEN field2 = concatenation expression

ELSE field1 still = NULL

My python skills are very rudimentary, and I have only tested off of what I've found through googling python IF/THEN statements.  I don't fully understand how to take their samples and make them work with what I need to accomplish.  One of the samples that I've tried to mimic is pasted below:

Expression:<BR />Reclass(!WELL_YIELD!)<BR /><BR />Expression Type:<BR />PYTHON_9.3<BR /><BR />Code Block:<BR />def Reclass(WellYield):<BR />&nbsp; if (WellYield >= 0 and WellYield <= 10):<BR />&nbsp; return 1<BR />&nbsp; elif (WellYield > 10 and WellYield <= 20):<BR />&nbsp; return 2<BR />&nbsp; elif (WellYield > 20 and WellYield <= 30):<BR />&nbsp; return 3<BR />&nbsp; elif (WellYield > 30):<BR />&nbsp; return 4

RichardFairhurst

In Python Null is None.  Use != instead of <>.  All if clauses and else clauses must end in a colon.

You don't set field values in a calculation you calculate a given field and return values to it.  If and else cannot be capitalized (capitalization and spacing matter in Python).  You must include all fields used for concatentation in the parameter list passed to the def of the method.  So your sample calculation should look like this (it will assign the concatenated value or Null (None) to field2):

Expression:

Reclass(!field1!, !Otherfield!)

Expression Type:

PYTHON_9.3

Code Block:

def Reclass(field1, otherfield):

    if field1 != None:

        return field1 + otherfield

    else:

        return None