Identify closed polylines in ArcGIS using Python

Question

Running ArcGIS 10.2 here and a complete beginner with Python. I'm trying to figure out a workflow to test for closed polylines using the field calculator. Essentially what I'd like to do is to populate a specific field with "closed" or "open". This is what I've come across and if I understand it correctly, it loops through each row and checks if the first x coordinate matches the last x coordinate, if there is a match then it prints the OID.

How do I convert this to a field calculator expression?

Do I need to use an update cursor rather than search to populate my new field?

fc = "Boundary" 
rows = arcpy.SearchCursor(fc) 
for row in rows: 
 geom = row.shape 
 if geom.firstPoint.X == geom.lastPoint.X: 
 print row.OBJECTID 
del row, row

• BBG_GIS: The answer is Yes. You need to use updatecursor rather than Searchcursor
• BBG_GIS: I think you'd better to compare x and y. You are using field calculator. You don't need fc, searchcursor or updatecursor in field calculator
• tigerwoulds: Can I do that without creating new fields with the start and end coordinates? @wetland
• BBG_GIS: Possible duplicate of arcpy: get list of adjacent lines per line
• Vince: Old-style cursors are archaic at this point -- Use DataAccess (arcpy.da) cursors for all your cursor needs.

Answer 1

enter image description here

You don't need to use a Cursor. Right-click the Field you want to populate, then enter this info into the Field Calculator.

Answer 2

I modified @klewis answer recently since I was running into an issue where some polylines had null geometry causing the field calculator to error out or give me false positives. Here is the updated code block:

def isClosed(geom):
 try:
 if geom.firstPoint.X == geom.lastpoint.X and geom.firstPoint.Y == geom.lastPoint.Y:
 return "1"
 else:
 return "0"
 except:
 return 'exception'