Question: I would like to update a field in a single feature class by a.) searching for a field where the values are not blank and b.) searching for a field where the values are blank. 

A typical scenario of this update would occur if there are two service requests in one feature class with the same service request number with one being updated. When the updated feature is in the feature class, it does not maintain all of the same values that the previous feature class held. The one field that I would like to update is `VehicleNam`. So if I have a feature class where SR # 555 appears twice, as OID1 and OID2, but only OID1 has a value for `VehicleNam` I would like to update the `VehicleNam` field in OID2 as well. Here is the script that I have so far, however an error is being thrown at line 5. I am using ArcGIS 10.2.2

`with arcpy.da.UpdateCursor(fc, ["VehicleNam"],"""VehicleNam <> ''""") as ucursor:
 with arcpy.da.SearchCursor(fc, ["VehicleNam"],"""VehicleNam = ''""") as scursor:
 for srow in scursor:
 svalue = srow[0]
 urow = ucursor.next() # instead of a full "for urow in ucursor" loop each time
 urow[0] = svalue
 ucursor.updateRow(urow)`

`Runtime error 
Traceback (most recent call last):
 File "<string>", line 5, in <module>
StopIteration`

Answer: 
Creating two cursors on the same feature class is going to be problematic. I'd create a dictionary of your matches first, and then iterate again and update.

Something like this (untested):

```
#SR field name
srField = "SR_FIELD_NAME"

vehNameDi = dict ([(sr, vehNam) for sr, vehName
                   in arcpy.da.SearchCursor
                   (fc, [srField, "VehicleNam"],"""VehicleNam <> ''""")])

with arcpy.da.UpdateCursor(fc, [srField, "VehicleNam"],"""VehicleNam = ''""") as cursor:
    for sr, vehNam in cursor:
        if not sr in vehNameDi:
            continue
        row = (sr, vehNameDi [sr])
        cursor.updateRow (row)

del cursor

```
Instead of:

```
urow = ucursor.next()

```

I think you should try:

```
urow = next(ucursor)

```

but also check the indentation on the last line of the code you presented.