How to use Python Pre-Logic in Field Calculator

Anonymous User

I am trying to use if/then python pre-logic in field calculator to only change the value of a field when one or two other fields equal a predefined value.  I can get it to work partially using the following code but it does not keep the original values for fields where "if=FALSE".  I have tried using "pass" but it does not seem to work the way I need it to.

Pre-logic:
def myfunc(SYMBOL,ID,OPER_MAINT_LEVEL):
    if ID == "4648" and OPER_MAINT_LEVEL == "1 - BASIC CUSTODIAL CARE (CLOSED)":
        return 4
    if ID == "4654":
        return 4
    if ID == "4663C" and OPER_MAINT_LEVEL == "1 - BASIC CUSTODIAL CARE (CLOSED)":
        return 4
    else:
        SYMBOL
SYMBOL=
myfunc( !SYMBOL!, !ID!, !OPER_MAINT_LEVEL! )

Anonymous User

Nulls are a little tricky. You could give something like this a try.

if not ID or not OPER_MAINT_LEVEL:
    return SYMBOL

Here is how I got it to work using str(!OPER_MAINT_LEVEL!):

def myfunc(SYMBOL,ID,OPER_MAINT_LEVEL):
    if not ID or not OPER_MAINT_LEVEL:
        return SYMBOL
    if ((ID == "4648" and OPER_MAINT_LEVEL == "1 - BASIC CUSTODIAL CARE (CLOSED)") or 
        (ID == "4654") or
        (ID == "4663C" and OPER_MAINT_LEVEL == "1 - BASIC CUSTODIAL CARE (CLOSED)")):
        return 4
    else:
        return SYMBOL

Expression:
SYMBOL =
myfunc(!SYMBOL!, !ID!, str(!OPER_MAINT_LEVEL!) )

Thanks for your help on this.