Setting default value for Python script tool properties using ArcPy?

Question

I have a model folder which contains several shapefile, but only one named oil.shp. Is there a way to automatically set the default value for the Add Oil Layer based on the model folder and the shapefile's name? It can be done by using os.path.join(model_folder, 'oil.shp') if I don't set Add Oil Layer as one parameter. However, I want to leave the parameter there in case someone else wants to play around with another oil.shp as needed. The Script Properties comes from the Script tool.

I am using ArcGIS Desktop 10.3.1 Advanced License.

Answer 1

To do this you would use tool validation. I recommend reviewing Understanding validation in script tools where the parts to pay attention to include:

Provide default values for parameters, such as cell size for rasters.

(it has a picture)

and

Internal validation doesn't do the following (but you can with your own validation code):

...

• Calculate default values.