Looping through a folder with Cell Statistics

Question

I have a folder with Day 1 Min, Day 1 Max and Day 2 Min, Day 2 Max...Day X Min, Day X Max rasters in it. I want to loop through this folder and use cell statistics on them to sum each day's min/max values (i.e. Day 1 Min + Day 1 Max).

I tried the following and got no results. Any pointers? How do I ensure that Cell Stats is summing the same days and not across multiple days?

MainFolder = r"C:\Users\uma.bhandaram\Desktop\2015\RasterCon2015"
for (path, dirs, files) in os.walk(MainFolder):
    for dir in dirs:
        env.workspace = os.path.join(path, dir)
        listRstrs = arcpy.ListRasters("Con.tif")
        for raster in listRstrs:
            rasterlist = []
            rasterlist.append(raster)
            outCellStats = CellStatistics(rasterlist, "SUM", "DATA")
            outCellStats.save(os.path.join(path, dir) + "Check.tif")

Answer 1

If I understand your question and more importantly the folder structure you are looping over correctly. You need to remove your actual call to CellStatistics to outside the loop where you are appending your rasters in.

There are a few other issues with this code per documentation here the input list to arcpy.CellStatistics needs to be of Layer, Raster, or Constant type. You were providing a list of paths to the raster. You need to convert the paths being looped over from listRstrs to arcpy.Raster and then add them to rasterlist. Further, you should not provide 'Con.tif' to the function arcpy.ListRasters this will only match rasters with that name. Once env.workspace is defined call arcpy.ListRaster and that will return all of the rasters within env.workspace

The corrected code should look something like this:

    env.workspace = os.path.join(path, dir)
    listRstrs = arcpy.ListRasters('*')
    rasterlist = []
    for path_to_raster in listRstrs:
        raster_dataset = arcpy.Raster(path_to_raster)            
        rasterlist.append(raster_dataset)
    outCellStats = CellStatistics(rasterlist, "SUM", "DATA")
    outCellStats.save(os.path.join(path, dir) + "Check.tif")

The way you were doing it was running CellStatistics each time a raster path, not arcpy.Raster as required, was added to rasterlist. So once for each raster path as well as for each raster path combination. However because you were providing the wildcard of 'Con.tif' to arcpy.ListRasters only one raster path, that of Con.tif was being looped over. By doing it how I have shown in the snippet above you are populating your list with the relevant arcpy.raster objects and then running CellStatistics on the fully populated list.