You could get a list of the featuredatasets using the ListDatasets
function, then loop through that list to get at the featureclasses within each featuredataset. From the docs:
datasetList = arcpy.ListDatasets("C*", "Feature")
for dataset in datasetList:
print dataset
If I understand your situation correctly, and assuming you have access to the Spatial Analyst extension and want to avoid implementing a coded solution, I think what you want is the tool "Mosaic to New Raster".
http://resources.arcgis.com/EN/HELP/MAIN/10.2/index.html#//001700000098000000
Just make the prompts match the original data (ex. pixel type, cell size, SRS, etc.) but for the "mosaic_method" parameter use "SUM".
Hope that works. Let me know if this is not what you were going for.
Edit (To work with ArcGIS 10.0):
To do this in ArcGIS 10.0 and below (when you don't have access to the SUM feature in Mosaic to New Raster) the following outlines a strategy that I think will work. Forgive me, it is a bit hard to test without myself having access to 10.0. Also, you will need the Spatial Analyst extension to use the below mentioned tools.
These doc pages should help you noodle out the solution:
Con
http://help.arcgis.com/EN/arcgisdesktop/10.0/help/index.html#//009z00000005000000.htm
Making Con expressions
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00p60000000p000000
Raster Calculator
http://help.arcgis.com/EN/arcgisdesktop/10.0/help/index.html#//009z000000z7000000.htm
So, the general workflow you will want is to either make an expression to be used in the Raster Calculator or to use a series of map algebra tools standalone (basically doing the steps from the raster calc manually and step by step). Whichever seems easiest for you.
I think you will want to do something like this with the Con tool:
in_conditional_raster = Raster(small_raster)
in_true_raster_or_constant = Raster({small_raster}) + Raster({big_raster})
in_false_raster_or_constant = Raster(big_raster)
where_clause = pretty sure this should just be left blank
So if all goes well, and I understand your datasets correctly, the above should search for areas that contain the small raster (true condition), if they find them they will create a new raster with the summed values of small_raster and big_raster. Then for areas not in the small_raster (false condition) it will just populate with values from the big_raster.
Hope this works!
Best Answer
The attached script which utilizes Raster Domain will work for you.
For a direct, non ESRI approach, check out Geospatial Modelling Environment's (GME) isectpntrst (Intersect Points With Raster).