Python Geoprocessing in ArcGIS 9.2 vs. 9.3

Michalis Avraam — Fri, 17 Jul 2009 07:20:39 +0000

There are some fundamental differences between geoprocessing performed in ArcGIS version 9.2 and 9.3. While I will not cover them all in this post, I will attempt to show the most fundamental differences that people seem to encounter more often.

The fundamental differences are as follows:

The method of invoking the geoprocessor is very similar for both, with the exception of an optional parameters when creating the object.
Geoprocessing methods do not return Python built-in data types but rather ESRI iterable objects.
Methods that used to return True/False values now return the Python True or False object rather than a string or 0/1.

The following table illustrates the differences:

ArcGIS version 9.2	ArcGIS version 9.3
gp = arcgisscripting.create()	gp = arcgisscripting.create(9.3)
# Create a list of available feature classes fcs = gp.ListFeatureClasses() # Iterate through said feature classes fcs.Reset() fc = fcs.Next() while fc: # Do work here fc = fcs.Next()	# Create a list of available feature classes fcs = gp.ListFeatureClasses() # Iterate through said feature classes for fc in fcs: # Do work here
# Identify the fields of a feature class dsc = gp.describe(fc) # Get the fields from the description flds = dsc.Fields # Iterate through the fields flds.Reset() field = flds.Next() while field: # Do work here field = flds.Next()	# Identify the files of a feature class dsc = gp.describe(fc) # Get the fields from the description flds = dsc.Fields # Iterate through the fields for field in flds: # Do work here
# Tell the geoprocessor to overwrite output by default. gp.OverWriteOutput = 1	# Tell the geoprocessor to overwrite output by default gp.OverWriteOutput = True

There is not list of commands that need the changes to the best of my knowledge. But a quick look through the Geoprocessor Programming Model for ArcGIS 9.2 can show which methods return an enumeration unit. In brief, ListDatasets, ListFeatureClasses, ListRasters, ListTables, ListWorkspaces, ListEnvironments, ListToolboxes, ListTools and all other methods that return an Array Object. For a complete listing of the changes, please read the ESRI document for Geoprocessor changes in 9.3.

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Geoprocessing Iteration with Python

Michalis Avraam » 9.3

Python Geoprocessing in ArcGIS 9.2 vs. 9.3