Programming ArcGIS 10.1 with Python Cookbook: This book provides the recipes you need to use Python with AcrGIS for more effective geoprocessing. Shortcuts, scripts, tools, and customizations put you in the driving seat and can dramatically speed up your workflow.

Geoprocessing tasks tend to be time consuming and repetitive, and often need to be run on a periodic basis. Frequently, many data layers and functions are involved. The ArcPy Python site package for ArcGIS provides a set of tools and execution environments that can be used to transform your data into meaningful results. Using scripts you can automate your geoprocessing tasks and schedule them to run when it is most convenient for your organization.

ArcGIS provides a geoprocessing framework for the purpose of automating your repetitive GIS tasks through a set of tools and execution environments for these tools. All tools operate on an input dataset, which you supply and transform in some way (depending upon the nature of the tool used) to produce a new output dataset. This new output dataset can then, if necessary, be used as the input dataset to additional geoprocessing tools in a larger workflow for your tasks. There are many tools provided by the ArcGIS geoprocessing framework...

In this recipe, you'll learn how to use the ArcGIS Python window. In Chapter 1, Fundamentals of the Python Language for ArcGIS, you learned how to use the IDLE development environment for Python, so this chapter will give you an alternative for writing your geoprocessing scripts. Either development environment can be used but it is common for people to start writing scripts with the ArcGIS Desktop Python window and then move on to IDLE when scripts become more complex. I should also mention that there are many other development environments that you may want to consider, including PythonWin, Wingware, Komodo, and others. The development environment you choose is really a matter of preference.

Before you can take advantage of all the geoprocessing functionality provided by ArcPy, you must first import the package into your script. This will always be the first line of code in every geoprocessing script that you write.

As an ArcGIS user, you have almost certainly used the many available tools in ArcToolbox to accomplish your geoprocessing tasks. Some examples include Clip, Buffer, Feature Class to Feature Class, Add Field, and many more. Your scripts can execute any of the tools found in ArcToolbox. Remember that the tools available to you as a programmer are dependent upon the license level of ArcGIS Destkop that you are using. These tasks can be automated through the creation of a Python script that executes these tools programmatically.

The ArcGIS Desktop help system is an excellent resource for obtaining information about any available tool. Each tool is described in detail on a unique page. The help system is available through ArcGIS Desktop or online.

In Chapter 1, Fundamentals of the Python Language for ArcGIS, we covered the topic of variables, so you should have a basic understanding of these structures. Variables are given a name and assigned a data value in your scripts. These named variables occupy space in your computer's memory and the data contained within these structures can change while a script is running. After the script has finished the memory space occupied by these variables is then released and can be used for other operations.

Up to this point, we have covered some basic concepts related to ArcPy. In addition to the basic ArcPy site package, there are a number of modules that you can use to access specific functionality. These modules must be specifically imported into your scripts before you can use the functionality provided. In this recipe, you will learn how to import these modules.