Open file (map) in python

[LB_994]

Hi! I feel like there might be something silly going on here,
but I have the following script:

riverFilename = "/HydroSheds/eu/eu_riv_30s.shp"
demFilename= "/HydroSheds/eu/eu_dem_30s"
setClone(riverFilename)
setClone(demFilename)

So I have a string here with the location of the files I want to use. I would like to get the attributes of the river and the dem file, but since it's a string I cannot 'read them in' yet. Therefore the setClone function doesn't work in this case. Does anyone know how python will recognize e.g. the 'eu_riv_30s.shp' map ?
Thanks!