Problem adding feature name to field in attribute table

Question

I have a small script that should take the name of the file and add it to a newly created field in several shapefiles.

import arcpy
arcpy.env.workspace = r"c:\users\athom\desktop\timber\New4"
arcpy.env.overwriteOutput = True
fcs = arcpy.ListFeatureClasses()
for fc in fcs:
 field = 'NAME'
 expression = str(fc)
 print expression
 arcpy.AddField_management(fc, field, "TEXT")
 arcpy.CalculateField_management(fc, field, "expression", "PYTHON")
del expression
del fc
del fcs

However, the file name of the first feature is written into the attribute table for each following features even though it shows in the python interpreter as the correct file name as "expression" - the attribute for NAME ends up being SA14107.shp in each shapefile.

python output

Why is the expression not being overwritten?

Answer 1

You need to pass the expression as a quoted string, like this:

arcpy.CalculateField_management(fc, field, "'" + expression + "'" , "PYTHON")