# How to use field calculator in this situation [closed]

How to use this formula in field calcultor in ArcMap. for example: A = Field1 B = Field2

``````  if A =<B
C = B
else:
C = A
``````
• Does this answer your question? Using conditional statements in ArcGIS Field Calculator?
– J.R
Apr 10, 2020 at 13:30
• Assuming neither value is `None` this is the same as the trivial Python expression `max(!A!,!B!)`. The documentation for Field Calculator has multiple examples, and the UI tool will help you build the function. Please make an attempt, then Edit the question to reflect any problem you may encounter. Apr 10, 2020 at 13:31

@Vince is right and this could be solved using the `max(!A!, !B!)` expression. However, if you had a more complex situation you could use a custom function. In Arcmap you can write a function on the code block space and then call it where you usually write the expression.

Your function (code block) could look something like:

``````my_function(field1_value, field2_value):
if field1_value <= field2_value:
return field2_value
else:
return field1_value
``````

Then you can call it using the following expression:

``````my_function(!A!, !B!)
``````

Of course, you need to specify Python as the parser.