topic Re: python beginner needs instant help calculating field in Python Questions

python beginner needs instant help calculating field

AMiller — Wed, 02 Dec 2015 21:04:28 GMT

Hi, I haven't yet learned how to use python, I know a tiny bit. I am using ArcMAp 10.2. I want to use a python program to Calculate a filed as a sequential ID, as I found instructions for in "Help" under calculate field examples (Accumulative and sequential calculations).

I am at a loss as to how to enter the info properly in the calculate field dialogue boxes. I have tried a few times, not at all sure where my basic problem lies. I need to do this real fast, but I just get lost or nowhere. Can you give my python future a quick boost? What do I type in the code block? what do I type in the other area? how do I have to alter the code for my scenario (from as it is typed in the help example?)

What type of field can I use for my new ID? I created a text field, is that ok?

Re: python beginner needs instant help calculating field

DanPatterson_Retired — Wed, 02 Dec 2015 21:11:05 GMT

I only have time for one question given your rush, this will at least get you started... integers should go in a numeric field with no decimal places

Re: python beginner needs instant help calculating field

AMiller — Wed, 02 Dec 2015 21:23:03 GMT

Thanks, will you have any time in near future? I may get to talk to ESRI tech support today, not sure. Thanks for clarifying the field requirement. I wanted to use text in my ID field, as I didn’t want the field to ever be calculated by mistake, but I suppose converting it to text might be another step.

Re: python beginner needs instant help calculating field

JoeBorgione — Wed, 02 Dec 2015 21:29:31 GMT

Do exactly what it says here and you'll be good to go. I just tried it:

38517 - Create sequential numbers in a field using Python in the Field Calculator

It looks something like this:

I just added a long int field named MyField to test.....

Re: python beginner needs instant help calculating field

AMiller — Wed, 02 Dec 2015 21:39:15 GMT

Thank you so much, I am about to try…

Adrienne

Re: python beginner needs instant help calculating field

AMiller — Wed, 02 Dec 2015 21:48:15 GMT

I tried and still not working, I tried a short integer field , and a long integer field. I tried with all records unselected, and I tried with all records selected.

Re: python beginner needs instant help calculating field

DanPatterson_Retired — Wed, 02 Dec 2015 21:49:44 GMT

and you made the field active by clicking on its title, prior to doing the field calculation... and you do have the code block specified?

Re: python beginner needs instant help calculating field

ChrisSmith7 — Wed, 02 Dec 2015 21:54:44 GMT

If you're having trouble auto-incrementing using Python, you can easily field calculate the FID or ObjectID field into your named ID field... if you need it to start at 1, just add 1 to your result, e.g. [FID] + 1

Re: python beginner needs instant help calculating field

DarrenWiens2 — Wed, 02 Dec 2015 22:00:53 GMT

What does the error (if any) in the Results window tell you was the problem?

Re: python beginner needs instant help calculating field

DarrenWiens2 — Wed, 02 Dec 2015 22:04:54 GMT

Of course, provided no FIDs are missing.

Re: python beginner needs instant help calculating field

AMiller — Wed, 02 Dec 2015 22:12:15 GMT

Thanks everyone, I was just on phone with ESRI tech support, I was having some kind of issue with my existing document, the directions sent by Joe Borgione worked when I (we) tried doing in a new document.

Problem solved!! Yay!! ☺

Re: python beginner needs instant help calculating field

AMiller — Wed, 02 Dec 2015 22:12:51 GMT

Problem solved!! Yay!! ☺

Re: python beginner needs instant help calculating field

AMiller — Wed, 02 Dec 2015 22:12:51 GMT

Problem solved!! Yay!! ☺

Re: python beginner needs instant help calculating field

AMiller — Wed, 02 Dec 2015 22:13:27 GMT

Problem solved!! Yay!! ☺

Re: python beginner needs instant help calculating field

ChrisSmith7 — Wed, 02 Dec 2015 22:16:35 GMT

Should be ok if they are calculating a shapefile field - as I understand, these are renumbered from 0 - no gaps will show-up. Of course, not the same for geodatabase!

Re: python beginner needs instant help calculating field

ChrisDonohue__GISP — Wed, 02 Dec 2015 22:24:11 GMT

To elaborate upon the suggestion by Darren Wiens ,here's how you check the Results for errors or other informational messages:

Here's the Results windows that comes up. Click on the plus signs to expand. Drill down to the specific run you did and then expand the Messages. If there is an error, there will be red x's. Oftentimes the Error message will have a link to further explain the error (though admittedly some links just say you got a generic error, which isn't much help).

Chris Donohue, GISP

Re: python beginner needs instant help calculating field

AMiller — Wed, 02 Dec 2015 22:33:51 GMT

Hi Darren, I did resolve my issue, with ESRI tech support. The problem I encountered at first (with instructions sent by Joe B) seemed to be resolved by trying the process in a new document. Thanks for your attention, appreciate it.

Re: python beginner needs instant help calculating field

AMiller — Wed, 02 Dec 2015 22:34:27 GMT

Yes, thank you.

Re: python beginner needs instant help calculating field

DavidAllen — Thu, 03 Dec 2015 17:09:24 GMT

Here's a little inside info that can benefit everyone wanting to do calculations in the field calculator using Python. The book "GIS Tutorial for Python Scripting" has a chapter on this ... AND YOU CAN GET THAT CHAPTER FOR FREE!

Go to this Esri Press site and click "Sample Chapter":

Esri Press | GIS Tutorial for Python Scripting

You can get the data necessary to do all the work for this book at this site and click under "Resources":

Esri Press Book Resources | GIS Tutorial for Python® Scripting

That'll get you started with Python - then you can buy the rest of the book later. By the time you finish all those tutorials and exercises you should be asking for a raise!

David W. Allen

Re: python beginner needs instant help calculating field

KathleenWallis — Thu, 03 Dec 2015 22:41:07 GMT

Although this document is a little dated, keep it in your files. You will find that you refer to it often.
Katy