Accessing parameter properties (within Python Toolbox) to make conditional statement work?

Question

I am creating a custom tool within a Python Toolbox framework using ArcGIS v10.4. The tool's behavior is dependent on the type of Input polygon chosen by the user (it can be shapefile, feature class, or a KML/KMZ file). I have attempted to create a conditional statement based on the datatype of the input polygon chosen by the user, yet my conditional statement isn't working. Pertinent code below:

if parameters[0].datatype == "File": #Convert KML to Shapefile
 arcpy.KMLToLayer_conversion(parameters[0].valueAsText, outputLocation, "OARS_Scratch") # Specify name of .gdb to be "OARS_Scratch.gdb"
 tempFC1 = outputLocation + os.path.sep + r"OARS_Scratch.gdb\Placemarks\Polygons" # "Placemarks" is the default feature database name created & "Polygons" is the default name after running KML conversion function
 tempFC2 = arcpy.env.scratchGDB + os.path.sep + "tempFC2"
 sr = arcpy.SpatialReference("NAD 1983 UTM Zone 13N") # Create spatial reference object
 arcpy.Project_management(tempFC1, tempFC2, sr, "WGS_1984_(ITRF00)_To_NAD_1983") # Project the new shapefile from WGS84 to NAD83 UTM Zone 13N & use the specified geographic transformation
 arcpy.FeatureClassToShapefile_conversion(tempFC2, outputLocation) # convert feature class to shapefile
 inputPolygon = outputLocation + os.path.sep + "tempFC2.shp"
 newfc = outputLocation + os.path.sep + str(userCustomNameEsri) + ".shp"
 arcpy.Append_management(inputPolygon, newfc, "NO_TEST") # Append shapefile from step above to template
 arcpy.Delete_management(outputLocation + os.path.sep + "OARS_Scratch.lyr") # Cleanup: delete both geodatabases, layer file, and temporary shapefile.
 arcpy.Delete_management(outputLocation + os.path.sep + "OARS_Scratch.gdb")
 arcpy.Delete_management(outputLocation + os.path.sep + "scratch.gdb")
 arcpy.Delete_management(outputLocation + os.path.sep + "tempFC2.shp")
elif parameters[0].datatype == "Feature Class" or "Shapefile":
 inputPolygon = parameters[0].value
 newfc = outputLocation + os.path.sep + str(userCustomNameEsri) + ".shp"
 arcpy.Append_management(inputPolygon, newfc, "NO_TEST")

When I try running the tool and choose a KMZ file, I get the following error:

Traceback (most recent call last):
File "<string>", line 431, in execute
File "c:\program files (x86)\arcgis\desktop10.4\arcpy\arcpy\management.py", line 3898, in Append
raise e
ExecuteError: Failed to execute. Parameters are not valid.
ERROR 000349: The input parameter is not a Table View
Failed to execute (Append).

Line 431 in my python toolbox script (.pyt) is the 3rd line after the "elif" statement shown above, which is what I want the tool to run if the input polygon is a shapefile/feature class (I don't want to run this for a KMZ file).

How do I fix my conditional statement? I must be accessing the object's properties incorrectly, but after trying attempting alternative approaches unsuccessfully (below), I'm at a loss.

if parameters[0].datatype == "DEFile":
 ...
elif parameters[0].datatype == "DEFeatureClass" or "DEShapefile":
 ...

OR

inputPolygon = parameters[0].value
if str(inputPolygon)[-4:] == ".KMZ" or "KML":
 ...
else:
 ...

This is how the parameter is defined earlier in my code:

def getParameterInfo(self):
 """Define parameter definitions"""
 param0 = arcpy.Parameter(
 displayName = "Input Polygon",
 name = "Input Polygon",
 datatype = ["DEFeatureClass", "DEShapefile", "DEFile"], # "DEFile" allows KML/KMZ files
 parameterType = "Required",
 direction = "Input")
 params = [param0]
 return params

Edited, new below - Additional troubleshooting info:

 arcpy.AddMessage("The datatype of parameter[0].datatype is {0}".format(parameters[0].datatype)) # [u'Feature Class', u'Shapefile', u'File']

When a shapefile is input:

 arcpy.AddMessage("The name of the file is {0}".format(parameters[0].value)) # C:\Documents\ArcGIS\New_Shapefile.shp
 inputPolygon = parameters[0].value
 arcpy.AddMessage("The name of inputPolygon is {0}".format(parameters[0].value)) # C:\Documents\ArcGIS\New_Shapefile.shp
 arcpy.AddMessage("The datatype of inputPolygon is {0}".format(type(inputPolygon))) # <type 'str'>
 arcpy.AddMessage("The last 4 characters of inputPolygon are {0}".format(str(inputPolygon)[-4:])) # .shp

When a KMZ file is input:

 arcpy.AddMessage("The name of the file is {0}".format(parameters[0].value)) # C:\Documents\ArcGIS\version1.kmz
 inputPolygon = parameters[0].value
 arcpy.AddMessage("The name of inputPolygon is {0}".format(parameters[0].value)) # C:\Documents\ArcGIS\version1.kmz
 arcpy.AddMessage("The datatype of inputPolygon is {0}".format(type(inputPolygon))) # <type 'str'>
 arcpy.AddMessage("The last 4 characters of inputPolygon are {0}".format(str(inputPolygon)[-4:])) # .kmz

• Midavalo: You possibly need to check the data type before your if and elif as you've told it that datatype = ["DEFeatureClass", "DEShapefile", "DEFile"] but it doesn't know the actual type when it gets to your if
• Edward: @Midvalo I don't believe that's the problem since the parameter doesn't have multiValue = True. The user will pick just one input polygon that could be one of those 3 datatypes, so the datatype would be decided based on the choice, or that's my assumption --- maybe I'm wrong. Please clarify if I'm misunderstanding your suggestion.
• Edward: @Midavalo. I ran arcpy.AddMessage("Datatype of the user input is {0}".format(parameters[0].datatype)) & you were right in that it returned [u'Feature Class', u'Shapefile', u'File']. Now just need to figure out how to properly use this information to inform the conditional statement.
• Midavalo: I suggest you edit your question to include that information and seek an answer for that

Answer 1

This code fixes the conditional statement & the code will correctly accept shapefiles / feature classes or KML/KMZ files.

 if str(inputPolygon)[-4:] == ".kmz" or str(inputPolygon)[-4:] == "kml":
 ...
 elif str(inputPolygon)[-4:] == ".shp":
 ...
 else:
 ...

An alternative approach of the 1st line suggested by Luke in the comments below that also works is

 if str(inputPolygon)[-4:] in (".kmz", ".kml"):
 ...

These code snippets are VERY similiar to one of the alternate approaches I had tried, which failed.

 if str(inputPolygon)[-4:] == ".kmz" or ".kml":

• user2856: if str(inputPolygon)[-4:] == ".kmz" or ".kml": will always return true. What that code is actually doing is checking if the first expression str(inputPolygon)[-4:] == ".kmz" is True then if that is False, it checks the expression after the or as a standalone expression. See boolean operations. A string with any value (i.e ".kml") will evaluate to True and an empty string will evaluate to False. You could do if str(inputPolygon)[-4:] in (".kmz", ".kml"): instead.