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:
arcpy.AddField_management(drainline, field, "TEXT", "", "", "20")
arcpy.CalculateField_management(drainline, field, '"' + drainline + '"', "")
arcpy.Statistics_analysis(drainline, outStatsTable, [["Shape_Length", "SUM"]], field)