Basic Field Calculations for ArcGIS®

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Tabular is an unofficial, interactive manual for the Calculate Field tool in ArcGIS Desktop. Tabular is designed for new GIS and Python users to learn scripting for spatial analysis.

You can copy-and-paste Python expressions into ArcGIS, navigate through the tool with screenshots, and test your code in Python sandboxes. Or you can download the cheat sheet.

Edit some text

Find characters

Goal	Code snippet------------------------------------------------------------------
Return the first character	`!fieldname![0]`
Return the first through third characters	`!fieldname![0:3]`
Return the second-to-last character	`!fieldname![-2]`

Remove characters

Goal	Code snippet
Remove all whitespace	`!fieldname!.rstrip()`
Swap certain words	`!fieldname!.replace("value", "New Value")`
Remove all non-alphanumeric characters	`‘’.join(ch for ch in !fieldname! if ch.isalnum())`
Return `<Null>`	`"None"`

Format the string

Goal	Code snippet-----------------------------------------------
Capitalize the string	`!fieldname!.capitalize()`
Convert the string to lowercase	`!fieldname!.lower()`
Convert the string to all caps	`!fieldname!.upper()`

Do some math

Add and subtract

Goal	Code snippet--------------------------------------------
Add 5 to the field value	`!fieldname! + 5`
Subtract 6 from the field value	`!fieldname! - 6`

Multiply and divide

Goal--------------------------------------	Code snippet--------------------------------------------
Multiply by 2	`!fieldname! * 2`
Divide by 3	`!fieldname! / 3`

Execute simple functions

In the Field Calculator, you can execute anything listed under Functions: or any built-in Python functions.

Goal	Code snippet---------------------------------
Calculate the logarithm	`math.log(!fieldname!)`
Round to 2 decimal places	`round(!fieldname!, 2)`

Deal with geometries

Find feature extents

Goal	Code snippet--------------------------------------------
Find the most extreme longitude	`!shape.extent.XMax!`
Find the most extreme latitude	`!shape.extent.YMax!`

Calculate line lengths

Goal	Code snippet----------------------------------------------------------
Calculate feature length in map units	`!shape.length!`
Calculate feature length in feet	`!shape.length@feet!`
Calculate feature length in geodesic feet	`!shape.length@Geodesicfeet!`

Compute shape areas

Goal	Code snippet---------------------------------------------------------------------
Calculate feature area in map units	`!shape.area!`
Calculate feature area in square feet	`!shape.area@squarefeet!`
Calculate feature area in geodesic square feet	`!shape.area@Geodesicsquarefeet!`