How to append summary statistics to dbf table

Question

I am working on a project to characterize watersheds where we are carrying out fieldwork. I am trying to use Summary Statistics to sum all the stream length channels contained in a watershed for multiple feature classes (drainline). Using arcpy.Statistics_analysis creates the output I want in a table but my script overwrites the table instead of adding the sum outputs to the table for each drainline feature. I am unable to figure out how to do this. My script on a subset of the data is below: # Set local variables ws_drainlines = arcpy.ListFeatureClasses("", "Line", "") outStatsTable = "C:/_LOCALdata/AB_ARCHYDRO/AB_ARCHYDRO_NOP.GDB/DrainageDensity" field = "Watershed" # Sum the drainline lengths for each DrainLine feature for drainline in ws_drainlines: print(drainline) arcpy.AddField_management(drainline, field, "TEXT", "", "", "20") arcpy.CalculateField_management(drainline, field, '"' + drainline + '"', "") arcpy.Statistics_analysis(drainline, outStatsTable, [["Shape_Length", "SUM"]], field) ‍‍‍‍‍‍‍‍‍‍‍‍‍

Myla-RaeBaldwin · Answer

Thanks Darren! I figured out how to name each table with the name of the drainline so that the tables all had unique names and were not overwritten. Then I created a list of all the tables and used the Merge_management to merge all of them into one master table. Works perfectly and is exactly what I needed.

DarrenWiens2 · Answer

Sure, there are lots of ways to do it. I was thinking just changing the output table name each time through, like below. Of course, you could substitute in your value for 'drainline' or whatever is most useful. Just so you realize the reason your table keeps getting overwritten is that if the name doesn't change, it overwrites the previous file. outStatsTable = "C:/_LOCALdata/AB_ARCHYDRO/AB_ARCHYDRO_NOP.GDB/DrainageDensity" for i in range(10): # numbers 0-9 print outStatsTable + str(i) C:/_LOCALdata/AB_ARCHYDRO/AB_ARCHYDRO_NOP.GDB/DrainageDensity0 C:/_LOCALdata/AB_ARCHYDRO/AB_ARCHYDRO_NOP.GDB/DrainageDensity1 C:/_LOCALdata/AB_ARCHYDRO/AB_ARCHYDRO_NOP.GDB/DrainageDensity2 C:/_LOCALdata/AB_ARCHYDRO/AB_ARCHYDRO_NOP.GDB/DrainageDensity3 C:/_LOCALdata/AB_ARCHYDRO/AB_ARCHYDRO_NOP.GDB/DrainageDensity4 C:/_LOCALdata/AB_ARCHYDRO/AB_ARCHYDRO_NOP.GDB/DrainageDensity5 C:/_LOCALdata/AB_ARCHYDRO/AB_ARCHYDRO_NOP.GDB/DrainageDensity6 C:/_LOCALdata/AB_ARCHYDRO/AB_ARCHYDRO_NOP.GDB/DrainageDensity7 C:/_LOCALdata/AB_ARCHYDRO/AB_ARCHYDRO_NOP.GDB/DrainageDensity8 C:/_LOCALdata/AB_ARCHYDRO/AB_ARCHYDRO_NOP.GDB/DrainageDensity9‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Myla-RaeBaldwin · Answer

Thanks Darren,

I tried to save each stats table with the drainline feature class that the stats was run on but I just kept overwriting the table. My workaround was to create a dictionary from the output tables and print the results in the Python Shell, which works for me for now. I put the following code after the last line of the code I first posted.

# Create dictionary
 d = {r[0]: r[1] for r in arcpy.da.SearchCursor(outStatsTable, fields)}

for key, val in d.items():
     print key,": ", val