topic Re: Removing Leading Numbers From a Field in ArcGIS Pro Questions

Removing Leading Numbers From a Field

jfkuhn — Thu, 28 Apr 2022 13:50:44 GMT

I have a tracts field (Tract) which I want to strip off the first 4 numbers in an attribute table. I created a new field (Tract2) for it. I've tried several commands without success using the field calculator. I'm receiving errors

Re: Removing Leading Numbers From a Field

jcarlson — Thu, 28 Apr 2022 14:57:37 GMT

What have you tried so far? And what errors do you get? What kind of field is it, string or numeric?

Assuming a string, you could try either of these approaches.

Arcade:

Right($feature.Tract, Count($feature.Tract) - 4)

Python:

 !Tract![4:]

Edit: Tweaked the Python bit. Thanks, Curt! Also, could @jfkuhn please elaborate on the intended output here? Do you want the first four characters to end up in the new field, or do you want the remaining characters after the first 4 are removed?

Re: Removing Leading Numbers From a Field

curtvprice — Thu, 28 Apr 2022 14:37:08 GMT

Census tract codes are text fields, so your syntax would work.

However, your code gets the last four numbers. To get the first 4 numbers you can use the Left function, or in python use the slice expression [:4].

Re: Removing Leading Numbers From a Field

jcarlson — Thu, 28 Apr 2022 14:55:41 GMT

D'oh! Thank you for catching that. Although, thinking about it more, it's not totally clear if "strip off" means that the first 4 numbers are being removed from the output, or if it's the first 4 that they want to keep. I guess [4:] would be the other way.

Re: Removing Leading Numbers From a Field

jfkuhn — Thu, 28 Apr 2022 15:18:00 GMT

1st 4 number will be removed

Re: Removing Leading Numbers From a Field

jfkuhn — Thu, 28 Apr 2022 15:21:35 GMT

Re: Removing Leading Numbers From a Field

curtvprice — Thu, 28 Apr 2022 15:25:00 GMT

I think this could be done in Arcade, but Python is MUCH easier for this task, use @jcarlson suggestion:

Tract[4:]

Re: Removing Leading Numbers From a Field

jcarlson — Thu, 28 Apr 2022 15:29:27 GMT

Ah, that usually happens if there's a null value in the sample row the tool uses to validate your expression. We need to be sure we handle null values in our expression.

Also, Left(string, x) returns the left-most x characters, so it's going to preserve the left characters, rather than remove them.

Try this:

var t = $feature['Tract'] if (IsEmpty(t)){ return '' } else { return Right(t, Count(t)-4) }

Re: Removing Leading Numbers From a Field

jfkuhn — Thu, 28 Apr 2022 15:30:38 GMT

For some reason what was suggested didn't work. See my screen capture

Re: Removing Leading Numbers From a Field

curtvprice — Thu, 28 Apr 2022 15:35:52 GMT

I hate that "circus language" with a white heat, but then I'm a desktop person (no JavaScript for me) and I'm old and hate being forced to learn yet another thing.

Python example:

# expression f(!Tract!) # code block def f(tract): try: return tract[4:] except: pass

Re: Removing Leading Numbers From a Field

jfkuhn — Thu, 28 Apr 2022 15:37:55 GMT

Still get errors. See attached

Re: Removing Leading Numbers From a Field

jcarlson — Thu, 28 Apr 2022 15:38:28 GMT

It's not horrible if you come from a JS background, but I would agree that if you've got the option to use Python, it's usually the better choice. "Couldn't I just use Python for this?" is something I utter pretty frequently when I'm working with web layers.

Re: Removing Leading Numbers From a Field

jcarlson — Thu, 28 Apr 2022 15:42:02 GMT

Hrm. Can you confirm whether tract is coming in as a string or number? In any case, try explicitly changing it. Replace line 1 of the expression with this:

var t = Text($feature['Tract'])

Re: Removing Leading Numbers From a Field

jfkuhn — Thu, 28 Apr 2022 15:44:38 GMT

curtvprice

Example also produced an error

Re: Removing Leading Numbers From a Field

curtvprice — Thu, 28 Apr 2022 15:51:24 GMT

Read the fine manual for the Calculate Field tool for more details on how to use the expression and code block.

Also if your tract is indeed a number (this is incorrect, you should try to get them read as text) you can string it to fix the problem, convert to string first, by wrapping the expression like this: f(str(!Tract!))

Make sure your Tract2 is a text field or you will lose leading zeros.

Re: Removing Leading Numbers From a Field

curtvprice — Thu, 28 Apr 2022 15:53:29 GMT

If your data are numbers, this Python expression should work without a code block. Assuming Tract2 is a text field, which it should be.

str(!Tract!)[4:]

Re: Removing Leading Numbers From a Field

jfkuhn — Thu, 28 Apr 2022 15:59:19 GMT

That work accept it puts a .0 at the end. I need it without a .0 so I can join it with another table

Re: Removing Leading Numbers From a Field

jfkuhn — Thu, 28 Apr 2022 16:01:14 GMT

The following work except it puts a .0 in at the end. I need it without the .0 so I can join it with another table.

If your data are numbers, this Python expression should work without a code block. Assuming Tract2 is a text field, which it should be.

str(!Tract!)[4:]

Add tags

Re: Removing Leading Numbers From a Field

jcarlson — Thu, 28 Apr 2022 16:08:28 GMT

str(!Tract!)[4:-2]

Can I ask where the original source of this data is? Did you by chance import a CSV or text file into Pro or something? It sounds an awful lot like a text-based data source being incorrectly interpreted as a number, which happens when a field only contains digits.

This is beyond the scope of the original question, but you may need to address upstream issues with how your data is imported. As @curtvprice notes, it really is supposed to be a text field.

Re: Removing Leading Numbers From a Field

jfkuhn — Thu, 28 Apr 2022 18:30:28 GMT

The original data source is numerical (double) so when I create a text field it puts .0 at the end. The data is a shape file. The .0 prevents me from joining it with the Census Tract data I downloaded. So, how can drop the .0 in the newly created text Tract Field from Python?