Getting values of last row in table with ArcPy/SearchCursor?

Question

I would like to base my query on the last row of a table? I know the basic syntax/functionality for my search cursor, how do I query only the last row;

Below is an example of my search criteria, this data comes from a log of success/fail for a script that runs, I will base other decisions off of the success or fail later in the application.

How do I add to my existing code the function to look in the last row, to getValue of timeand success or fail

I am using ArcGIS 10.2.

cursor = arcpy.SearchCursor(aTable,"""Time > DATEADD(minute, -2,  GETDATE())""")
for row in cursor:
    print(row.getValue("Time"))
if row.getValue("Time") < datetime.datetime.now().strftime('%m/%d/%Y %H:%M:%S'):
    print "true"
else:
    print "false"

This is later implemented in the script and creates the success or fail values as yes and norespectively.

rows = arcpy.InsertCursor(aTable)
for x in xrange(0, outputobjects):
    row = rows.newRow()
    row.setValue("Success", 'YES')
    row.setValue("Fail", 'NO')
    row.setValue("Time", Start)
    rows.insertRow(row)

Answer 1

I would usually suggest the da.SearchCursor as well, but its order by clause only works withe data in a database. So, if it is in a database:

a_table = "YourTable"
order_fld = "Time"
return_flds = ["Time", "SomeOtherField"]
where_str = """Time > DATEADD(minute, -2,  GETDATE())"""

sql_clause = (None,'ORDER BY {} DESC'.format(order_fld))

last_row = ''
last_time = ''
with arcpy.da.SearchCursor(a_table, return_flds, where_clause=where_str, sql_clause=sql_clause) as cursor:
  last_row = cursor.next()
  last_time = last_row[0]

Else, if it is a shapefile:

sort_string = "{} D".format(order_fld)
arcpy.SearchCursor(a_table, where_clause=where_str, sort_fields=sort_string)
last_row = cursor.next()
last_time = last_row.Time

Both of these, you don't have to loop through the entire result to get the "last" row. By ordering by descending, the last row is the 1st row, and you can move on.

Answer 2

If you're using 10.2, I would first recommend using the data analysis version of the search cursor. Then you can use python's list comprehension to get the last value.

Try something like the code below. It creates a list of all values in the 'time' field, and then accesses the last record through indexing (the [-1] at the end of the list comprehension line).

#Time field name
TimeFld = "Time"

#List comprehension and data analysis search cursor
LastTimeValue = [r[0] for r in arcpy.da.SearchCursor(aTable, TimeFld)][-1]

#Logic check
if LastTimeValue < datetime.datetime.now().strftime('%m/%d/%Y %H:%M:%S'):
    print "true"
else:
    print "false"

Answer 3

You can do this with a Search Cursor wrapped in a list comprehension:

import arcpy

# Your input shp of fc  
fc = r'C:\path\to\your.shp'

# List all of the row values as a list of tuples
rows = [row for row in arcpy.da.SearchCursor(fc, "*")]

# Get the last row
print rows[-1]

Answer 4

Another idea, though all these answers should work. This will avoid having to iterate the whole cursor. Not sure if the sql_clause will decrease performance though:

oid_field = "OBJECTID"
sql = ("ORDER BY {0} D".format(oid_field),"")
with arcpy.da.SearchCursor(table,"*",sql_clause=sql) as cursor:
    for row in cursor:
        last_row = row
        break

The object id field name depends on the type of dataset you're working with, but the highest value will always be the last row. This cursor will be sorted descending by object id, and then you only have to iterate the first row. I haven't tested this though...