Introduction to ArcPy

Topics What is ArcPy? Accessing geoprocessing tools using ArcPy Writing scripts using ArcPy

What is ArcPy? ArcPy was introduced with ArcGIS10 It’s Python site package With ArcPy, you’ve access to the – Geoprocessing tools – Extensions – Functions & classes

Access to Geoprocessing Tools ArcPy provides access to all geoprocessing tools - Based on license level Tools return an object Tools can also produce messages -- Object & messages can be manipulated from Python script

ArcPy Functions Functions perform a specific task as a part of larger program All geoprocessing tools are functions -- Union, Buffer, Clip etc. But not all functions are geoprocessing tools -- List datasets, describe dataset, create cursor

ArcPy Classes Classes provide a framework for creating object - referred to as an instance Examples of classes - SpatialReference, Extent etc. Classes have methods & properties -- Spatialreference.name -Spatialreference.type

ArcPy Modules Modules are Python libraries containing functions and classes 3 modules --Mapping modules: arcpy.mapping - Spatial Analyst module: arcpy.sa - Geostatistical module: arcpy.ga Example: -- arcpy.sa.Slope is same as using the Slope tool from Spatial Analyst toolbox

How to use ArcPy You have to import the ArcPy package before using it Simply type “import arcpy” in Python Window in ArcGIS

How to use a tool? Two ways to call a tool Example: arcpy.Buffer_analysis() Example: arcpy.analysis.Buffer()

Tool Syntax Each tool needs specific parameters to run correctly Buffer_analysis (in_features, out_feature_class, buffer_distance_or_field, {line_side}, {line_end_type}, {dissolve_option}, {dissolve_field}) Buffer tool needs 3 required parameters: 1.Input features 2.Out feature class 3.Buffer distance There are a number of optional parameters too!!

Environment Setting Set your workspace pathname for reading input & writing output file: arcpy.env.workspace = “C:\\GIS222” arcpy.env.workspace = “C:\\Test.gdb” # Read and write files from GIS222 folder # Read and write files from Test.gdb arcpy.env.overwriteOutput = 1 # Will overwrite the output file

Let’s try it! a.Run buffer in Python Window b.Write a script to run buffer in PythinWin

Using List Functions

Topics How to get a list of data layers? Iterate through the list

Getting a list Getting the list of available data is often the first step of many tasks ArcPy provides functions for getting − Lists of fields − Lists of datasets − List of feature classes − List of Files − List of Tables − And more

Important Note YOU MUST set the workspace before calling any list function import arcpy arcpy.env.workspace = "C:\\temp" fcs = arcpy.ListFeatureClasses()

Iterating through the list Python ‘for’ loop can be used to loop through your list import arcpy arcpy.env.workspace = “C:\\Auburn.gdb” for fc in arcpy.ListFeatureClasses(): print fc

Other List Methods ListDatasets –Lists all datasets from a workspace –Feature, TIN, Raster, or CAD ListRasters –Lists all rasters in a workspace –PNG, TIFF, JPG, BMP, GIF, IMG, GRID, others ListFields –Lists the fields in a feature class, shapefile, or table in a specified dataset ListTables –Lists all tables in the workspace ListWorkspaces –Lists workspaces within a workspace –Folders, file geodatabases, personal geodatabases

Let’s try it!