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Update Cursor skipping last row?

Randomly select a record to update using arcpy.da.UpdateCursorCalculate Row if Row Value Equals Value in ListCursor update row operatorParsing Attribute TableIdentify closed polylines in ArcGIS using PythonIteratively Updating Just Bottom Row in Table using ArcPy?Comparing value with value from the next rowPython time condition within Calculate FieldArcPy rollback update / insert cursors if error occursSwitching from Nested Search Cursors to Dictionaries

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2

0

I have created a python function within field calculator to calculate the time difference between a timestamp (yyyy-MM-dd HH:mm:ss) in a row and the row after (the interval field in seconds). I have used a update cursor with field calculator to do this, however I am receiving null values for both the first and last row.

The first is correctly missed due to the function being reliant on having a value set by the previous row.

I am unsure as to why the last row is being skipped?

I have had this issue on several other update cursor functions including those on simple single row condition statements.

Am I missing a statement to close the update cursor loop?

My code is:

import arcpy, time, datetime
from time import strftime
from datetime import timedelta, datetime
from arcpy import da

def FindTime(table,date,interval):

 firstRow = True

 with arcpy.da.UpdateCursor(table, ["interval", "date"]) as cursor:

 for row in cursor:
 gap2 = row[2]

 if firstRow == True:
 gap1 = gap2
 firstRow = False
 continue
 timedelta = gap2 - gap1
 row[0] = timedelta.days * 24 * 3600 + timedelta.seconds
 gap1 = gap2 
 cursor.updateRow(row)

arcpy modelbuilder field-calculator cursor python-parser

share|improve this question

edited 35 mins ago

Will

asked 4 hours ago

WillWill

544

add a comment | 

2

0

I have created a python function within field calculator to calculate the time difference between a timestamp (yyyy-MM-dd HH:mm:ss) in a row and the row after (the interval field in seconds). I have used a update cursor with field calculator to do this, however I am receiving null values for both the first and last row.

The first is correctly missed due to the function being reliant on having a value set by the previous row.

I am unsure as to why the last row is being skipped?

I have had this issue on several other update cursor functions including those on simple single row condition statements.

Am I missing a statement to close the update cursor loop?

My code is:

import arcpy, time, datetime
from time import strftime
from datetime import timedelta, datetime
from arcpy import da

def FindTime(table,date,interval):

 firstRow = True

 with arcpy.da.UpdateCursor(table, ["interval", "date"]) as cursor:

 for row in cursor:
 gap2 = row[2]

 if firstRow == True:
 gap1 = gap2
 firstRow = False
 continue
 timedelta = gap2 - gap1
 row[0] = timedelta.days * 24 * 3600 + timedelta.seconds
 gap1 = gap2 
 cursor.updateRow(row)

arcpy modelbuilder field-calculator cursor python-parser

share|improve this question

edited 35 mins ago

Will

asked 4 hours ago

WillWill

544

add a comment | 

I have created a python function within field calculator to calculate the time difference between a timestamp (yyyy-MM-dd HH:mm:ss) in a row and the row after (the interval field in seconds). I have used a update cursor with field calculator to do this, however I am receiving null values for both the first and last row.

The first is correctly missed due to the function being reliant on having a value set by the previous row.

I am unsure as to why the last row is being skipped?

I have had this issue on several other update cursor functions including those on simple single row condition statements.

Am I missing a statement to close the update cursor loop?

My code is:

import arcpy, time, datetime
from time import strftime
from datetime import timedelta, datetime
from arcpy import da

def FindTime(table,date,interval):

 firstRow = True

 with arcpy.da.UpdateCursor(table, ["interval", "date"]) as cursor:

 for row in cursor:
 gap2 = row[2]

 if firstRow == True:
 gap1 = gap2
 firstRow = False
 continue
 timedelta = gap2 - gap1
 row[0] = timedelta.days * 24 * 3600 + timedelta.seconds
 gap1 = gap2 
 cursor.updateRow(row)

arcpy modelbuilder field-calculator cursor python-parser

share|improve this question

edited 35 mins ago

Will

asked 4 hours ago

WillWill

544

import arcpy, time, datetime
from time import strftime
from datetime import timedelta, datetime
from arcpy import da

def FindTime(table,date,interval):

 firstRow = True

 with arcpy.da.UpdateCursor(table, ["interval", "date"]) as cursor:

 for row in cursor:
 gap2 = row[2]

 if firstRow == True:
 gap1 = gap2
 firstRow = False
 continue
 timedelta = gap2 - gap1
 row[0] = timedelta.days * 24 * 3600 + timedelta.seconds
 gap1 = gap2 
 cursor.updateRow(row)

share|improve this question

edited 35 mins ago

Will

asked 4 hours ago

WillWill

544

share|improve this question

edited 35 mins ago

Will

asked 4 hours ago

WillWill

544

asked 4 hours ago

WillWill

544

asked 4 hours ago

WillWill

544

1 Answer
1

active

oldest

votes

2

If your field is type date, code below should work. Last line is not calculated since there is no row after. Or do you want to calculate for example second rows diff as second row-first row?

import arcpy

fc = 'somedates'
datefield = 'date123'
daydiff_field = 'seconddiff_long'

all_dates = [i[0] for i in arcpy.da.SearchCursor(fc,datefield)]

diff = [(d1-d0).seconds for d0,d1 in zip(all_dates, all_dates[1:])]
givediff = iter(diff)

with arcpy.da.UpdateCursor(fc, daydiff_field) as cursor:
#next(cursor) #uncomment this line if you want to calculate row2 diff as row2-row1, =first row no diff
 for row in cursor:
 try:
 row[0] = next(givediff) #Fetch diffs until list is empty...
 cursor.updateRow(row)
 except StopIteration: #...then break the cursor
 break

share|improve this answer

edited 26 mins ago

answered 4 hours ago

BERABERA

17k62044

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  This is why I love using SE, I have never used the iter() function before, had to go away and look it up, like it! Is there a performance boost using that approach or was it for convenience?
  
  – Hornbydd
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Nice! Dont know if there is a performance boost. I use it because it is a simple way of fetching items in a list instead of trying to iterate over a cursor and list at the same time.
  
  – BERA
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  If anything, it will actually be slower, because the table is traversed twice instead of once. But for small tables that may not be an issue.
  
  – Berend
  43 mins ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Slower than what approach?
  
  – BERA
  41 mins ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Slower than using just an update cursor, as OP does
  
  – Berend
  41 mins ago
  

  
  
  
  

add a comment | 

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2

If your field is type date, code below should work. Last line is not calculated since there is no row after. Or do you want to calculate for example second rows diff as second row-first row?

import arcpy

fc = 'somedates'
datefield = 'date123'
daydiff_field = 'seconddiff_long'

all_dates = [i[0] for i in arcpy.da.SearchCursor(fc,datefield)]

diff = [(d1-d0).seconds for d0,d1 in zip(all_dates, all_dates[1:])]
givediff = iter(diff)

with arcpy.da.UpdateCursor(fc, daydiff_field) as cursor:
#next(cursor) #uncomment this line if you want to calculate row2 diff as row2-row1, =first row no diff
 for row in cursor:
 try:
 row[0] = next(givediff) #Fetch diffs until list is empty...
 cursor.updateRow(row)
 except StopIteration: #...then break the cursor
 break

share|improve this answer

edited 26 mins ago

answered 4 hours ago

BERABERA

17k62044

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  This is why I love using SE, I have never used the iter() function before, had to go away and look it up, like it! Is there a performance boost using that approach or was it for convenience?
  
  – Hornbydd
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Nice! Dont know if there is a performance boost. I use it because it is a simple way of fetching items in a list instead of trying to iterate over a cursor and list at the same time.
  
  – BERA
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  If anything, it will actually be slower, because the table is traversed twice instead of once. But for small tables that may not be an issue.
  
  – Berend
  43 mins ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Slower than what approach?
  
  – BERA
  41 mins ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Slower than using just an update cursor, as OP does
  
  – Berend
  41 mins ago
  

  
  
  
  

add a comment | 

2

If your field is type date, code below should work. Last line is not calculated since there is no row after. Or do you want to calculate for example second rows diff as second row-first row?

import arcpy

fc = 'somedates'
datefield = 'date123'
daydiff_field = 'seconddiff_long'

all_dates = [i[0] for i in arcpy.da.SearchCursor(fc,datefield)]

diff = [(d1-d0).seconds for d0,d1 in zip(all_dates, all_dates[1:])]
givediff = iter(diff)

with arcpy.da.UpdateCursor(fc, daydiff_field) as cursor:
#next(cursor) #uncomment this line if you want to calculate row2 diff as row2-row1, =first row no diff
 for row in cursor:
 try:
 row[0] = next(givediff) #Fetch diffs until list is empty...
 cursor.updateRow(row)
 except StopIteration: #...then break the cursor
 break

share|improve this answer

edited 26 mins ago

answered 4 hours ago

BERABERA

17k62044

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  This is why I love using SE, I have never used the iter() function before, had to go away and look it up, like it! Is there a performance boost using that approach or was it for convenience?
  
  – Hornbydd
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Nice! Dont know if there is a performance boost. I use it because it is a simple way of fetching items in a list instead of trying to iterate over a cursor and list at the same time.
  
  – BERA
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  If anything, it will actually be slower, because the table is traversed twice instead of once. But for small tables that may not be an issue.
  
  – Berend
  43 mins ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Slower than what approach?
  
  – BERA
  41 mins ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Slower than using just an update cursor, as OP does
  
  – Berend
  41 mins ago
  

  
  
  
  

add a comment | 

If your field is type date, code below should work. Last line is not calculated since there is no row after. Or do you want to calculate for example second rows diff as second row-first row?

import arcpy

fc = 'somedates'
datefield = 'date123'
daydiff_field = 'seconddiff_long'

all_dates = [i[0] for i in arcpy.da.SearchCursor(fc,datefield)]

diff = [(d1-d0).seconds for d0,d1 in zip(all_dates, all_dates[1:])]
givediff = iter(diff)

with arcpy.da.UpdateCursor(fc, daydiff_field) as cursor:
#next(cursor) #uncomment this line if you want to calculate row2 diff as row2-row1, =first row no diff
 for row in cursor:
 try:
 row[0] = next(givediff) #Fetch diffs until list is empty...
 cursor.updateRow(row)
 except StopIteration: #...then break the cursor
 break

share|improve this answer

edited 26 mins ago

answered 4 hours ago

BERABERA

17k62044

import arcpy

fc = 'somedates'
datefield = 'date123'
daydiff_field = 'seconddiff_long'

all_dates = [i[0] for i in arcpy.da.SearchCursor(fc,datefield)]

diff = [(d1-d0).seconds for d0,d1 in zip(all_dates, all_dates[1:])]
givediff = iter(diff)

with arcpy.da.UpdateCursor(fc, daydiff_field) as cursor:
#next(cursor) #uncomment this line if you want to calculate row2 diff as row2-row1, =first row no diff
 for row in cursor:
 try:
 row[0] = next(givediff) #Fetch diffs until list is empty...
 cursor.updateRow(row)
 except StopIteration: #...then break the cursor
 break

share|improve this answer

edited 26 mins ago

answered 4 hours ago

BERABERA

17k62044

answered 4 hours ago

BERABERA

17k62044

answered 4 hours ago

BERABERA

17k62044