Hi, First of all, I have been using ArcGIS 10 for a long time but I am a novice to using Python scripting. So please pardon my probably rather clunky code.What I would like to do for each feature is to update a field with the mean value of a different field (in the same feature class) of all features that fall within a certain radius. In my case, I have the point shapefile "FL20C.shp" which contains 20 features each with a series of attributes including "ZBUSH" and "MEAN01". I would like to update "MEAN01" with the value calculated by taking the mean/average of all the features in a 150 km radius of it (including the feature to be updated itself). The layer "counties_lyr" is the Feature Layer I created to be able to run the SelectLayerByLocation. (So that step has already been made and is left out of the script.)I have tested the different blocks of code and they seem to work: the script iterates successfully through the SelectLayerByLocation and the steps of calculating the mean. I think the problem lies in establishing the connection between the UpdateCursor and the SearchCursor used in the SelectLayerByLocation. I have structured the code in different ways, hitting road blocks in different locations. With this first attempt I get the following error: "Runtime error <class 'arcgisscripting.ExecuteError'>: ERROR 999999: Error executing function. Cannot acquire a lock. Cannot acquire a lock. [The table FL20C.shp is being written by another process.] Failed to execute (SelectLayerByLocation)." This error results from the following code: import arcpy
# Creating the UpdateCursor and its input
counties = "C:/GISDATA2/FAUI/USAtests/FL20C.shp"
cursor01 = arcpy.UpdateCursor(counties)
# Setting up variables to be used in the Select Layer By Location
selectionbase = arcpy.SearchCursor("counties_lyr")
desc = arcpy.Describe("counties_lyr")
selectionbaseShapeFieldName = desc.featureClass.shapeFieldName
# Starting the iteration through the input table that is to be updated
for county in cursor01:
# Starting the Select Layer By Location
selected_c = arcpy.SelectLayerByLocation_management("counties_lyr", "WITHIN_A_DISTANCE", row.getValue(selectionbaseShapeFieldName), "150000 Meter", "NEW_SELECTION")
# Counting the number of selected features to be used in the calculation of the Mean
selected_nr = arcpy.GetCount_management(selected_c)
selected_count = selected_nr.getOutput(0)
count_sel = float(selected_count)
# Calculating the total of the ZBUSH value to be used in the Mean
curs_selected = arcpy.SearchCursor(selected_c)
list4total = []
for co in curs_selected:
list4total.append(co.ZBUSH)
total_v = sum(list4total)
new_mean = total_v / count_sel
# Update "MEAN01" with the new_mean value
county.MEAN01 = new_mean
cursor01.updateRow(county)
# emptying variables before restarting loop
del count_sel
del list4total
del total_v
del new_mean
del cursor02
Alternatively this code runs the Select Layer By Location and the Calculations successfully, but fails to update the Row. Instead I get: Runtime error <type 'exceptions.AttributeError'>: 'Cursor' object has no attribute '__exit__'I think my mistake is in this code segment of the full code that follows below: with arcpy.UpdateCursor(counties) as cursor02:
for co in cursor02:
co.MEAN01 = new_mean
cursor02.updateRow(co)
Should I leave out the iteration? How do I make sure that the shapefile-row being updated in this cursor corresponds to the row in the FeatureLayer used for the SelectLayerByLocation? If this is done through a SQL statement, then I don't know where to place it or how to state it. import arcpy
selectionbase = arcpy.SearchCursor("counties_lyr")
desc = arcpy.Describe("counties_lyr")
selectionbaseShapeFieldName = desc.featureClass.shapeFieldName
for row in selectionbase:
# Make the selection
selected_c = arcpy.SelectLayerByLocation_management("counties_lyr", "WITHIN_A_DISTANCE", row.getValue(selectionbaseShapeFieldName), "150000 Meter", "NEW_SELECTION")
# Count the number of selected features
selected_nr = arcpy.GetCount_management(selected_c)
selected_count = selected_nr.getOutput(0)
count_sel = float(selected_count)
# Get the total ZBUSH value for the selected features
curs_selected = arcpy.SearchCursor(selected_c)
list4total = []
for county in curs_selected:
list4total.append(county.ZBUSH)
total_v = sum(list4total)
new_mean = total_v / count_sel
# Write the mean-value to the feature
with arcpy.UpdateCursor(counties) as cursor02:
for co in cursor02:
co.MEAN01 = new_mean
cursor02.updateRow(co)
# Reset values at end of iteration
del count_sel
del list4total
del total_v
del new_mean
Thank you in advance for your help! Vincent
