Performing Union_analysis on outputs created with arcpy.GetParameterAsText()?

Question

I am trying to write a script tool for my geospatial programming class and I am stuck (this is an online course and we get NO support from our instructor).

What I need to do is create buffers (different values) around three different features, these are set up as parameters that the user will define. I got this to work just fine.

Next, I need to perform a Union_analysis on those three buffer outputs, this is where I am getting stuck. I did this in a previous script, where I was using known feature classes, but I cannot figure out how to get this to recognize the outputs of the three "user selected" features.

Here is my script so far:

import arcpy

arcpy.env.overwriteOutput = True
buffered_area = "buffered_area"

# Get the input parameters for the Buffer tool
inPath = arcpy.GetParameterAsText(0) 
outPath = arcpy.GetParameterAsText(1)
bufferDistance = arcpy.GetParameterAsText(2)
inPath1 = arcpy.GetParameterAsText(3)
outPath1 = arcpy.GetParameterAsText(4)
bufferDistance1 = arcpy.GetParameterAsText(5)
inPath2 = arcpy.GetParameterAsText(6)
outPath2 = arcpy.GetParameterAsText(7)
bufferDistance2 = arcpy.GetParameterAsText(8)

# Run the Buffer tool
buffer1 = arcpy.Buffer_analysis(inPath, outPath, bufferDistance)
buffer2 = arcpy.Buffer_analysis(inPath1, outPath1, bufferDistance1)
buffer3 = arcpy.Buffer_analysis(inPath2, outPath2, bufferDistance2)

arcpy.Union_analysis("buffer1 #; buffer2 #; buffer3 #", buffered_area, "ALL", "", "GAPS")

And here is the error message I get:

Failed script Script1...

Traceback (most recent call last):
  File "\\SNHU-LABS-UTIL2.snhu-labs.com\userprofiles$\william.herzig\Documents\programming\try.py", line 29, in <module>
    arcpy.Union_analysis("buffer1 #; buffer2 #; buffer3 #", buffered_area, "ALL", "", "GAPS")
  File "c:\program files (x86)\arcgis\desktop10.6\arcpy\arcpy\analysis.py", line 629, in Union
    raise e
ExecuteError: Failed to execute. Parameters are not valid.
ERROR 000732: Input Features: Dataset buffer1 #;buffer2 #;buffer3 # does not exist or is not supported
WARNING 000725: Output Feature Class: Dataset \\SNHU-LABS-UTIL2.snhu-labs.com\userprofiles$\william.herzig\Documents\ArcGIS\Default.gdb\buffered_area already exists.
Failed to execute (Union).

Failed to execute (Script1).

Answer 1

Try instead to put your list of buffered outputs into a list object. You might also set the workspace option before proceeded, otherwise ArcMap will send the output from the union to the default geodatabase.

arcpy.env.workspace = "path to output folder or geodatabase"
arcpy.Union_analysis([buffer1, buffer2, buffer3], buffered_area)

Or if you know the path is working you can use the output from the parameter.

arcpy.Union_analysis([outPath, outPath1, outPath2], buffered_area)

Answer 2

buffer1, 2 and 3 are result objects not the buffer outputs. Try:

arcpy.Union_analysis([outpath, outPath1, outPath2], buffered_area, "ALL", "", "GAPS")