Single Formula expression to retrieve comma-separated values from a List Box

[Scott_Snowman]

I am attempting to use a List Box to generate a comma-separated list of values that have been selected. That part is easy enough

1. Use the results of the List Box selection to update a Text Input tool
2. Split the cell to rows with a comma delimiter
3. Filter to rows that contain "=True"
4. Use a Formula to remove the "=True" strings from the values
5. Summarize with the Concatenate option to get a comma-separated list of checked values.

See example screen shot. As expected, the output of the final node is 'parameter1,parameter3,parameter4'

However -- is there a way to do this in a single Formula expression? (It'd have to involve RegEx, I'm sure.)

My goal is to use the comma-separated list in combination with the Action Tool's "Update Value with Formula" option to directly supply the comma-separated list to another tool in the macro.

[lmorrell]

Hi @Scott_Snowman,

replace(regex_replace([A], '(\,)*\w*?=False(\,)*', ''), '=True', '')

This formula replaces all the values that equal false using regex, and then replace the '=True' string with a regular replace. 

Hope this helps neaten up the workflow!

[Scott_Snowman · Accepted solution]

@lmorrell truly, it should be said that with a long enough RegEx expression and a place to stand, one can move the world. (Or, perhaps at least replace it with something more desirable.)

I definitely need to study more RegEx. Thank you so much!

That being said this looks just slightly off. I get the following with a test string:

parameter1=True,parameter2=True,parameter3=False,parameter4=True

parameter1,parameter2parameter4

The comma before the final parameter always seems to be missing and my attempts to fix it weren't successful.

Any ideas?

Edit: By changing the provided RegEx to the below, I'm left with what I need but a trailing comma at the end if I have any True parameters before any False parameters. That's easily Trimmed away.

\w*?=False(\,)*

So this looks like it should work:

TrimRight(replace(regex_replace([A], '\w*?=False(\,)*', ''), '=True', ''),',')

[Scott_Snowman]

@lmorrell if my edited solution makes sense, and you would like to adjust your original response to include, I'll gladly mark it as the Solution.

Thank you!!