Field Calculator Expression Inside a Python Script

DamonOsbourne

Ok, imagine there are 3 fields in a table: Field1, Field2, and and empty Field3. All I want to do is multiply Field1 * Field2 and populate the result in Field3. This is easily done in the field calculator in ArcMap, but what does the code look like in a python script? I am assuming that the arcpy tool I need is Calculate Field, but am not 100% certain. The part I am stuck on is what does the 'expression' look like in the code line below... or if a different tool is better, what is it?

CalculateField_management (in_table, field, expression, {expression_type}, {code_block})

jskinner

Hi Damon,

It would look something like the below:

arcpy.CalculateField_management(featureclass, "field3", "!field1! * !field2!", "PYTHON_9.3","#")

One good trick that you can do is execute the tool in ArcMap, then go to your Results window.  Here you can right-click on the results > Copy As Python Snippet.

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