Creating IDs for multiple features in Python Parser of ArcGIS Field Calculator?

Question

Does anyone know how to create ID numbers for multiple features using python?

For example; (IDs being the object ID, Name and object ID being two different fields)

Names //// IDs

Street 01

River 02

Mountain 03

Hill 04

Names //// Desired IDs;

Street 01

River 01

Mountain 02

River 02

I was hoping to write a code in the Python Parser of the field calculator, as I have over 3 thousand points, every three needing the same ID. I need to have each three consecutive entries given the same numeric ID, in a new field.

Answer 1

I'm assuming that instead of the second "River" value (under desired ID) you mean "Hill".

In the Field Calculator window (for your new field), select the Python parser (in the parser box in the top left of the window), and enter the following into the expression:

{"Street": 01, "River": 01, "Mountain": 02, "Hill":02}[!names!]

What this does is create a dictionary, and specifically return the value for the key as specified by the !names! field. If your field with the text value (street, river, etc) is not called "names" just type in your field name between the exclamation points; ArcMap uses exclamation points in python to identify field name values.