Calculate Date field in ArcPy

Question

I'm trying to use arcpy.ExtractValuesToPoints() to get raster values to a points feature class for several raster files (8760). The goal is to get a time-slice view of how the values at certain locations change over time.

I'm fairly well versed in Python as well as the built-in datetime module. The trouble that I'm having is saving the date-time values to a table in ArcGIS.

(I've gotten a similar approach to work using arcpy.da.InsertCursor() but this approach is very process-intensive and I've concluded that it isn't a viable approach for what I'm trying to do. Plus I'd rather not re-invent the wheel and use the ArcGIS function: ExtractValuesToPoints() instead.)

To give a little background, I'm using dates that require datetime precision to the hour so I've elected to use a File Geodatabase to accommodate that feature (since shapefiles can only handle the date portion).

I'm trying to solve for a single case as I can create a solution for iterating over the 8760 files that I'm working with.

So far this is what I have:

import arcpy
import os
GRID_Table = "E:\HRRR.gdb\GRID_Table" # GRID_Table is an ArcGIS table
SPP_LMP_Points = "E:\HRRR.gdb\SPP\SPP_LMP_Points" # that contains datetime and 
out_path = "C:\scratch.gdb" # raster_path pairs.
row1 = [] # Get date_time and raster_path 
for row in arcpy.SearchCursor(GRID_Table): # from every entry in GRID_Table
 row1.append((row.DateTime, row.RasterPath)) #
date_time = row1[0][0] # Set date_time to the first 
raster_path = row1[0][1] # entry 
out_path_shp = os.path.join(out_path, os.path.basename(raster_path)) # Generate 
 # output path.
arcpy.sa.ExtractValuesToPoints(SPP_LMP_Points, raster_path, out_path_shp)
arcpy.AddField_management(out_path_shp, "DateTime", "DATE")
arcpy.CalculateField_management(out_path_shp, "DateTime", 
 "!DateTime! = {0}".format(date_time), 
 "PYTHON_9.3")

This all works fine and doesn't report any exceptions or errors. The trouble that I'm having is that the call to arcpy.CalculateField_management() doesn't populate the DateTime field. Instead I get a NULL value in the table.

Any thoughts?

• nmpeterson: Have you considered using an InsertCursor instead of CalculateField_management?
• Emil Brundage: What do you get when you do a print date_time prior to your field calculate?
• Chad Cooper: Possibly a datatype mismatch? Your field DateTime is a DATE field, but are passing string to in CalculateField maybe?
• John C. King: nmpeterson - I have tried the InsertCursor() and I've gotten it to work. The trouble is that I'm working with a fairly large set of data and accessing each feature line-by-line isn't feasible.
• John C. King: Emil Brundage - print date_time gives me the standard __str__() output from a datetime object (ie 2014年12月20日 11:00:00). If I type print(type(date_time)) I get <type 'datetime.datetime'>.

Answer 1

You just don't quite have the quotes right in your expression.You need double quotes around your datetime. Also, you shouldn't have !DateTime! = as part of it.

Try:

arcpy.CalculateField_management(out_path_shp, "DateTime", 
 '"' + date_time + '"', 
 "PYTHON_9.3")

• John C. King: Emil - Great suggestion. This wasn't exactly the answer but I was able to use this snippet to get done what I was intending. I'll give this a +1 but check my answer for the solution.

Answer 2

Based on Emil's response below I was able to find a sufficient answer.

I used Emil's code, verbatim, and was able to get the following error: "TypeError: cannot concatenate 'str' and 'datetime.datetime' objects"

The final solution is as follows (note the str() call):

arcpy.CalculateField_management(out_path_shp, "DateTime", 
 '"' + str(date_time) + '"', 
 "PYTHON_9.3")

To clarify, the above code enters the datetime information into an ArcGIS "date" featureclass field.