Arcpy.da.UpdateCursor, Error - Sequence size must match size of row

Question

I am trying to use an UpdateCursor fill in a field but I keep getting an error, can anyone tell me what I am doing wrong? My code is below:

import arcpy
fc= "C:\Users\Keri\Desktop\GEP_690\Project Data\FINAL_PROJECT.gdb\NYC_Demographics_2010"
with arcpy.da.UpdateCursor(fc, ["Total1","White","Pct_White"]) as cursor:
 for field in cursor:
 if field[0]==0:
 field[2]=0
 else:
 field[2] = field[1] / field[0]
 cursor.updateRow([field])
print "Complete."
del row
del cursor

This is the error I keep getting:

Traceback (most recent call last):
 File "C:\Python27\ArcGIS10.2\Lib\site-packages\pythonwin\pywin\framework\scriptutils.py", line 326, in RunScript
 exec codeObject in __main__.__dict__
 File "C:\GEP_662\Lab9.py", line 15, in <module>
 cursor.updateRow([field])
TypeError: sequence size must match size of the row

• Aaron: As a side note, del row and del cursor are not needed when using a cursor in a with statement.
• Keri: Thank you for your insight, I did not know that, just learning python

Answer 1

Use the cursor.updateRow(field) instead of cursor.updateRow([field]). You should supply an object, not the list.

• mr.adam: This will solve the problem, but to be a little more specific, field already is a list (an update cursor returns a set of lists, one per row). When you write [field] you are actually passing a list with one a single entry, and that entry is a list, e.g. [['field1','field2']].
• Keri: Thank you Mr.adamn, Now I see why I was getting that error message. You were so helpful!!!!!