Replace Null Value - Field Calc, Python

[KeithSoRelle]

Trying to replace a null value with the field calculator. I am have a script that appends multiple feature classes into one feature class. After each feature class appends I want to add a field calculateField_management (field calculator) statement run that makes all null values from a specific field into a string value. 

I've tried a number of ways but have yet to get an expected result. 

I have 2 values for in the field - Null, 'CFW' and need to replace Null with 'TAR'.

Then I will have 3 values - Null, 'CFW', 'TAR' and will need to replace Null with 'DEN'

I've been trying something along the lines of:

def myCalc(x)

      if (x != 'CFW"):

         return 'TAR'

else:

      return 'CFW'

Should be simple but I haven't had much luck getting the expected response. Could use help on both field calculations.

Thanks,

-Keith 

[DanPatterson_Retired]

if x is None:‍

    do something

should work if it is truly none and not just an empty string

or to cover all bases (add more to the tuple if needed

if x in (None, "", " ", "nadda"):‍

    do something 

[JoshuaBixby · Accepted solution]

You can use Python Conditional expressions, a.k.a., ternary operators, to accomplish this task on one line.  Set the parser to Python and put the following in the expression box:

'TAR' if !Field! is None else !Field!‍

Swap !Field! above for your field.

[KeithSoRelle]

Worked well. Thanks for the help!