Using ModelBuilder/ArcPy in ArcGIS Pro to Iterate Field Values of Multiple Feature Classes?

Question

I am using ArcGIS Pro 2.01 for this task.

I have 114 shapefiles (each represents a session of the US Congress) which include every congressional district since 1790. I have added a short integer field to each feature class called "Congress". This field is intended to signify which session of Congress that feature was used for. For example, all 435 features in the shapefile representing the 114th Congress should have a value of 114 for that field.

I am trying to automate the entire process using ModelBuilder. I do understand that this could be done in Python but I would prefer to use the ModelBuilder so that I can teach my high school GIS class how to do this before showing them the code.

Each shapefile contains the Congressional session number at the end of the filename.

Should I try to use the For tool or should I use something like the Iterate Field Value tool?

Answer 1

To do this I would create a model which iterates field values in one feature class, and then make that model a submodel of another model that iterates feature classes.

The help for this is at:

• Iterate Feature Classes
• Iterate Field Values

It is much easier to do in ArcPy.

• SteveC: I will definitely look into the scripting option but I would like to be able to associate the visual nature of ModelBuilder with my students. At first glance it appears that it is not possible to run two iterators at the same time in the same model as one is greyed out as soon as the other is set up.
• PolyGeo: Exactly, that is why I think you need one iterator in your submodel, and the other in your model (that contains the submodel).
• SteveC: Looks like I need to spend some more time learning ArcPy.
• PolyGeo: We've had lots of ModelBuilder questions on incorporating submodels if you are looking for help doing that.

Answer 2

I was able to work through this using ArcPy:

1. Created an array called "CD_List" containting filepath names for all 114 feature classes. This was simple enough to create in Excel with the CONCATENATE formula.
2. Used a for loop to iterate the process with the Calculate Field Tool:

for x in range (0, 113): arcpy.CalculateField_management(CD_List[x],"Congress",(x+1),"","")