Problem with if-statement and whereClause format

Question

I have a program which should count the number of a feature class or the length of a feature class depending on the geometry of the input feature class. This part is working. There are two parameter-fields. One dropdown-field (optional) where you can choose a fieldname of the feature class and the other is a parameter field (optional) where you can choose a value depending on the fieldname which was chosen. If I put in values in both optional parameter fields, the number or the length of the feature class should be count by using the inputvalues in a SQL-expression (whereClause). If I am trying to do that, I get following error: IndexError: tuple index out of range in line:

whereClause = whereClause.format(arcpy.AddFieldDelimiters(fc_clipped, fieldname))

Second problem: Why are both fields optional? Because if I don't put in any value to both optional parameters, the number of the feature class should be count (without a whereClause) with GetCountManagement. But the code is still running through the else-statement and I get an error because of leaving the fieldname-parameter empty even though the parameter is optional.

So what I need is that the SQL-Expressions works with the input-parameters and if the input-parameters are empty it should just use the GetCountManagement.

That is the full code:

 fc_clipped = os.path.join(out_gebietsscharfe_Objekte, objektname)+"_"+gebietsname #input feature
 fn = parameters[2].valueAsText #fieldname
 if arcpy.Describe(fc_clipped).shapeType == "Point" or "Polygon":
 if parameters[2].valueAsText == "#":
 COUNTER = arcpy.GetCount_management(fc_clipped)
 else:
 COUNTER = 0
 whereClause = """{} = '{}'"""
 whereClause = whereClause.format(arcpy.AddFieldDelimiters(fc_clipped, fn))
 for row in arcpy.da.SearchCursor(fc_clipped, fn, whereClause):
 COUNTER+=1
 else:
 fn = "Shape_Length"
 COUNTER = 0
 whereClause = """{} = '{}'"""
 whereClause = whereClause.format(arcpy.AddFieldDelimiters(fc_clipped, fn))
 for row in arcpy.da.SearchCursor(fc_clipped, fn, whereClause):
 COUNTER+=row[0]
 arcpy.AddMessage(COUNTER)

• blabbath: Normally SQL 'OR' requieres you to write: if arcpy.Describe(fc_clipped).shapeType == "Point" OR arcpy.Describe(fc_clipped).shapeType == "Polygon"
• Andreas: @blabbath Thanks for your response but that is not the issue in the program. It works with 'or'
• Vince: No, it doesn't. You need to be careful with Boolean expressions in Python, because or nonZero will always result in True. @blabbath is correct
• user2856: arcpy.Describe(fc_clipped).shapeType == "Point" or "Polygon" will always return True. If you had a line feature class, it would return True. You need arcpy.Describe(fc_clipped).shapeType == "Point" or arcpy.Describe(fc_clipped).shapeType == "Polygon"` OR arcpy.Describe(fc_clipped).shapeType in ("Point" , "Polygon")

Answer 1

As @blabbath has mentioned this line of code isn't doing what you'd like it to do:

if arcpy.Describe(fc_clipped).shapeType == "Point" or "Polygon":

This statement will always return True regardless of what arcpy.Describe(fc_clipped).shapeType returns:

>>> if 1 + 7 == 50 or 12:
 print "hello world"
hello world

Think of it like this:

if (1 + 7 == 50) OR (12)

1 + 7 does not equal 50, but 12 returns True.

Alternatives:

>>> if 1 + 7 == 50 or 1 + 7 == 12:
 print "hello world"
>>> if 1 + 7 in (50, 12):
 print "hello world"
>>> 

Your fix:

if arcpy.Describe(fc_clipped).shapeType in ("Point", "Polygon"):

• Andreas: Yes, you are all right with it. Thank you!
• Paul: This is because non-empty strings are "Truthy".