CreateFeatureClass_management (simple question)

Question

I was asked about a seemingly simple line of code in one of my scripts and I didn't have an immediate answer. After a few pages of g-search, I'm still a bit stumped, but not afraid to ask for the answer! facFC = arcpy.CreateFeatureclass_management("in_memory", "facFC", "POINT")[0]‍ What exactly is the [0] at the end of this statement for? There's examples of having it there and other examples it's not found. Thanks!

XanderBakker · Answer

I second what Dan_Patterson mentioned. I normally define the output and other variable at the start of the script and use in this case the os module to split the path and name in a path and a name. Something like this: import arcpy import os fc_out = r'C:\some\path o\outputfgdb.gdb\YourFeatureclass' ws, fc_name = os.path.split(fc_out) arcpy.CreateFeatureclass_management(ws, fc_name, etc) arcpy.AddField_management(fc_out, YourFieldName, etc)‍‍‍‍‍‍‍‍‍

bixb0012 · Answer

As Darren points out, nearly all geoprocessing tools return Result—Help | ArcGIS Desktop objects, which explains the ArcGIS/ArcPy side of your question.

For the Python side of your question, Python classes can emulate container objects by implementing certain special methods:  3. Data model - Emulating Container Types— Python 2.7.15 documentation.  Support for the indexing and slicing operator, i.e., [], is implemented using the object.__getitem__ special method.  For the ArcPy Result object, the __getitem__ special method either points to Result.getOutput() or implements the same code.

In short, Result[0] is the same as calling Result.getOutput(0) .

DarrenWiens2 · Answer

I believe the [0] indicates the first item in the Result object returned from the tool, which happens to be the new feature class name.

Using tools in Python—Geoprocessing and Python | ArcGIS Desktop