5/4/2023 0 Comments Arcmap model builderModelBuilder contains a number of elements called Iterators that can do looping in various ways. Looping is a key concept in computer programming, and you will use it often as you write Python scripts for this course. A main benefit of computers is their ability to quickly repeat tasks that would otherwise be mundane, cumbersome, or error-prone for a human to repeat and record. Looping, or iteration, is the act of repeating a process. Some of the concepts in them are easier to understand once you've worked with geoprocessing for a while. I suggest reading them once now and returning to them occasionally throughout the course. The following topics from Esri go into more detail on intermediate data and are important to understand as you work with the geoprocessing framework. You can specify that a tool write to the scratch geodatabase by using the %scratchgdb% variable in the path. Unless the user has changed it, the scratch geodatabase will be found at C:\Users\\Documents\ArcGIS\scratch.gdb on Windows 7/8. A scratch geodatabase is one that is guaranteed to exist on all ArcGIS installations. This is where the concept of the scratch geodatabase (or scratch folder for file-based data like shapefiles) environment variable can come in handy. When running a model on another file system, specifying paths as we did above can be problematic since the folder structure is not likely to be the same. If, on the other hand, the model is run from ModelBuilder, intermediate datasets are left in their specified locations. Esri has programmed ModelBuilder's default behavior such that when a model is run from a GUI interface, all datasets besides the final output - referred to as intermediate data - are automatically deleted. ![]() ![]() Most of the tools that you run produce an output dataset, and when you chain many tools together, those datasets start piling up on disk. ![]() Some of the items are common to the ArcGIS geoprocessing framework, meaning that they also apply when writing Python scripts with ArcGIS. This is particularly helpful if you anticipate using ModelBuilder frequently in your employment. This page of the lesson contains some optional advanced material that you can read about ModelBuilder. By now, you've had some practice with ModelBuilder, and you're about ready to get started with Python.
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