Hi Dan,
The NREL NSRDB API delivers solar resource data in a file. I don't think there is a way to get the data from the API without downloading a file.
The FetchResourceFiles() function downloads the data as a CSV file, but it is possible to get it as a JSON file instead. For example, you can see the documentation of the PSM v3 endpoint here:
developer.nrel.gov/docs/solar/nsrdb/psm3-download/
The 'pvsamv1' module has two ways of inputting weather data, as documented in
nrel-pysam.readthedocs.io/en/master/modules/Pvsamv1.html. You can read it from a weather file in the SAM CSV format by setting the value of 'solar_resource_file' to the file's path and name, or you can use the 'solar_resource_data' input to set the values without reading them from a file.
Best regards,
Paul.