Python script to iterate through geodatabase and assign field value based on spatial location

Question

I have two types of spatial data. One is a geodatabase of parcel data by county in Florida, and the other is a shapefile containing wind_zones through out Florida (used for enforcing certain building codes). I want to create and populate two fields in the parcel data based on which county and which wind_zone they are in. I have found a post here: Assigning field value based on location without join that answers a similar question and is what I am basing my code off of, but I need to iterate this process through an entire geodatabase that contains ~70 counties. Is there a line of code that can be added to iterate through the geodatabase so I do not have to manually run the code for each county?

Here is the code I have so far:

import arcpy

# Set overwrite option
arcpy.env.overwriteOutput = True

# KEEPING ORIGINAL LAYERS (NOT CREATING ADDITIONAL "JOINED" LAYER)
# Create FeatureLayers
arcpy.MakeFeatureLayer_management("C:/Data/HAAS/parc_join/parcels_1.gdb",    "lyr_parcels")
arcpy.MakeFeatureLayer_management("C:/wind_zones/All_WZs.shp", "lyr_windZones")

# Add a "LOCATED_WZ" & "WZ_CAT" field
arcpy.AddField_management("lyr_parcels", "Located_WZ", "TEXT", "", "", "20")
arcpy.AddField_management("lyr_parcels", "WZ_Cat", "SHORT")


# Create a search cursor for the WZs
rows = arcpy.SearchCursor("lyr_windZones")
for row in rows:
# What you'll do is select each WZ one at a time, and then select all the parcels in that WZ and calculate the "LOCATED_WZ" field 
# NOTE: If you are using not using shapefiles, then you'll have to change the FID in the line below to OBJECTID (or similar)
    arcpy.SelectLayerByAttribute_management("lyr_windZones", "NEW_SELECTION", "\"FID\" = " + str(row.getValue("FID")))
    arcpy.SelectLayerByLocation_management("lyr_Parcels", "INTERSECT", "lyr_windZones", "", "NEW_SELECTION")
    arcpy.CalculateField_management("lyr_parcels", "Located_WZ", "'{0}'".format(str(row.getValue("COUNTY"))), "PYTHON_9.3", "")
    print "Finished processing " + str(row.getValue("COUNTY"))

# Create a search cursor for the WZs
rows = arcpy.SearchCursor("lyr_windZones")
for row in rows:
# What you'll do is select each WZ one at a time, and then select all the parcels in that WZ and calculate the fields 
# NOTE: If you are using not using shapefiles, then you'll have to change the FID in the line below to OBJECTID (or similar)
    arcpy.SelectLayerByAttribute_management("lyr_windZones", "NEW_SELECTION", "\"FID\" = " + str(row.getValue("FID")))
    arcpy.SelectLayerByLocation_management("lyr_Parcels", "INTERSECT", "lyr_windZones", "", "NEW_SELECTION")
    arcpy.CalculateField_management("lyr_parcels", "WZ_Cat", "'{0}'".format(str(row.getValue("DESCRIPT"))), "PYTHON_9.3", "")
    print "Finished processing " + str(row.getValue("DESCRIPT"))

Because each county is it's own feature class, I suppose I don't need to add a new field to tell me county name, because I will already know which county it is in.

Answer 1

Regardless of the decision you take to choose how you'll add the information from the wind zones to your parcels in case a parcel intrsects more than one wind zone: you can use arcpy.ListFeatureClasses() to list all your parcels feature classes, then iterate over the feature classes with a for loop and run your code for each of them:

import arcpy

# Set overwrite option
arcpy.env.overwriteOutput = True

# Define your workspace. This should be your database with parcels feature class
arcpy.env.workspace = r"C\Data\HAAS\parc_join\parcels.gdb"

# This can be done once for all iterations
arcpy.MakeFeatureLayer_management("C:/wind_zones/All_WZs.shp", "lyr_windZones")

for fc in arcpy.ListFeatureClasses():

    # KEEPING ORIGINAL LAYERS (NOT CREATING ADDITIONAL "JOINED" LAYER)
    # Create FeatureLayers
    arcpy.MakeFeatureLayer_management(fc, "lyr_parcels")
    ...

Be careful, there is an error in your code in this line:

arcpy.MakeFeatureLayer_management("C:/Data/HAAS/parc_join/parcels_1.gdb",    "lyr_parcels")

The input of MakeFeatureLayer is a feature class, not a gdb.

Other attention points:

• use arcpy.da.Cursors with a with statement, not the old arcpy.Cursors, especially if you're overwriting them (using with deletes the cursor automatically when they've run).
• you can calculate both fields with one cursor, no need to use 2.