Time difference between two string fields with microsecond (or seconds) resolution using, Arcpy, datatime and UpdateCursor

Question

I am trying to calculate (using Arcpy) the time difference between two fields that are in string data type and they have the following time format "YYY-MM-DD HH:mm:SS.sss"

I have achieved that between two fields with data type "Datetime" with the following script,

import arcpy
from arcpy import da
import datetime
in_table = arcpy.GetParameterAsText(0)
out_table = arcpy.GetParameterAsText(1)
#define table into dictionary
tf = datetime.datetime.strptime([row[0] for row in arcpy.da.SearchCursor(in_table, ["TimeFinal"])], "%Y-%m%-%d %H:%M:%S.%f")
ti = datetime.datetime.strptime([row[0] for row in arcpy.da.SearchCursor(in_table, ["TimeInitial"])], "%Y-%m%-%d %H:%M:%S.%f")
#set firstRow variable to zero
counter = 1
index = 0
with arcpy.da.UpdateCursor(in_table, ["TimeDiff"]) as cursor:
     for row in cursor:
         if index<=len(ti)-2:
         n0 = ti[index]
         n1 = tf[index+1]
         if n1 >= n0:
             row[0] = int((n1 - n0).total_seconds())
         else:
             counter+=1
         cursor.updateRow(row)
         index+=1
         else:
         cursor.updateRow(row)
         break
with arcpy.da.UpdateCursor(in_table, ["TimeDiff"]) as cursor:
      for row in cursor:
          if row[0] == None:
              cursor.deleteRow()
          else:
              cursor.updateRow(row)
arcpy.CopyRows_management(in_table, out_table)

When I try to read the fields using update cursor using datetime.strptime the script send the error "strptime() argument 1 must be str, not list", does anyone know another approach to calculate the time difference in seconds or microseconds?

Answer 1

This line...

datetime.datetime.strptime([row[0] for row in arcpy.da.SearchCursor(in_table, ["TimeFinal"])], "%Y-%m%-%d %H:%M:%S.%f")

...is invalid (as is the similar line after it). As the error says, you are passing a list as the first argument to datetime.datetime.strptime() which expects a single string for the first argument.

To see what you are actually passing as the first argument, add this line just before it:

print([row[0] for row in arcpy.da.SearchCursor(in_table, ["TimeFinal"])

It will print a list with one value for each record in the database cursor. You cannot pass this list to datetime.datetime.strptime(). It needs a single string.

If you are wanting to get a list of dates for each of those two lists of strings, you could do it like this:

tf = [datetime.datetime.strptime(row[0], "%Y-%m%-%d %H:%M:%S.%f") for row in arcpy.da.SearchCursor(in_table, ["TimeFinal"])]
ti = [datetime.datetime.strptime(row[0], "%Y-%m%-%d %H:%M:%S.%f") for row in arcpy.da.SearchCursor(in_table, ["TimeInitial"])]

Do a web search for python list comprehension to read some explanations of how the 'list comprehension' syntax works in Python.