topic Re: cursor compare last und actual row in Python Questions

cursor compare last und actual row

UrsRichard — Thu, 10 Sep 2015 12:25:45 GMT

How can I iterate trough a cursor an compare the last row with the actual?

def disolveOemDolungen(bnum):

unterlieger = None

pCursor = arcpy.UpdateCursor(oemFC, "BNUM = '" + bnum + "'","","von; bis; klasse, key","von A; bis A")

row = pCursor.next()

while row:

if not unterlieger is None:

if (unterlieger.getValue("klasse") == 7):

arcpy.AddMessage("Oberlieger:" + unterlieger.getValue("key"))

if (math.fabs(unterlieger.getValue("bis") - row.getValue("von")) <= 1):

unterlieger.setValue("klasse", row.getValue("klasse"))

unterlieger.setValue("sbreite", row.getValue("sbreite"))

pCursor.updateRow(unterlieger)

arcpy.AddMessage("Dissolve mit Oberlieger: " + unterlieger.getValue("key"))

if row.getValue("klasse") == 7:

if not unterlieger is None:

arcpy.AddMessage("Unterlieger " + row.getValue("key"))

if (math.fabs(unterlieger.getValue("bis") - row.getValue("von")) <= 1):

row.setValue("klasse", unterlieger.getValue("klasse"))

row.setValue("sbreite", unterlieger.getValue("sbreite"))

pCursor.updateRow(row)

arcpy.AddMessage("Dissolve mit Unterlieger: " + row.getValue("key"))

unterlieger = row

row = pCursor.next()

Row and unterlieger contains always the same Object. Therefore I can't compare the rows. How can this be done with Python?

Re: cursor compare last und actual row

WesMiller — Thu, 10 Sep 2015 12:28:28 GMT

Are you wanting to compare attributes from row to row? Read a row into a list or dictionary then when you get to the next row compare and repeat.

Re: cursor compare last und actual row

UrsRichard — Thu, 10 Sep 2015 12:34:11 GMT

In Some cases I have to store values in the "last" Row. So the Values in a List are not enough. I need the Row object.

Re: cursor compare last und actual row

WesMiller — Thu, 10 Sep 2015 12:37:50 GMT

Have you looked at make feature layer as an option to hold the single row? You could hold it row by row or multiple rows if you needed.

Re: cursor compare last und actual row

UrsRichard — Thu, 10 Sep 2015 15:42:47 GMT

Could you give me an example how I can get hold of multiple rows with make fature layer?

Re: cursor compare last und actual row

ThomasEmge — Sun, 12 Dec 2021 01:02:06 GMT

It is because of the type of row the arcpy.UpdateCursor is returning. Have you looked into the data access module?

http://desktop.arcgis.com/en/desktop/latest/analyze/arcpy-data-access/what-is-the-data-access-module-.htm

The da module offers better performance as well as a more pythonic experience. For example it is returning the rows as dictionaries.

So this would work:

>>> with arcpy.da.UpdateCursor("mydata", "*") as cursor:
...     old = None
...     for row in cursor:
...         if old is not None:
...             print row[0], old[0]
...         old = row

Re: cursor compare last und actual row

WesMiller — Sun, 12 Dec 2021 01:02:10 GMT

import arcpy
fc = "Your Feature Class"
desc = arcpy.Describe(fc)
oidfld = desc.OIDFieldName
fld = arcpy.AddFieldDelimiters(fc,oidfld)
print oidfld,fld
with arcpy.da.SearchCursor(fc, ("OID@")) as cursor:
    for row in cursor:
        tmplyr = "tmplyr"+str(row[0])
        #You could create a list of features here to input below
        query = fld + " in (" + str(row[0]) + ")"
        arcpy.MakeFeatureLayer_management(fc,tmplyr,query)

Re: cursor compare last und actual row

RhettZufelt — Sun, 12 Dec 2021 01:02:13 GMT

Not exactly what you need, but I've used this to look for missing and/or duplicate values in the field [recnum], and if there are blanks or duplicates, replace with the next sequential number.

Like I said, not exactly what you are after, but I had this and thought you might get some ideas from it.

def FixDuplicates():
    global rec
    rec = 0
    maxValue = arcpy.SearchCursor(infc, "", "", "", "recnum D").next().getValue(myField) #Get 1st row in descending cursor sort
    if maxValue == None:
        maxValue = 0
    newValue = maxValue + 1
    uCur = arcpy.UpdateCursor(infc, "", "", "", "recnum A")
    for row in uCur:
        if row.getValue('recnum')  and row.getValue('recnum') != 0:
                  curRec = row.getValue('recnum')
                  #First if checks
                  #if the row's rec is equal to the previous row
                  if curRec != rec:
                      rec = row.getValue('recnum')
                  #If its rec is not
                  #equal to the previous row then we are ready to update the existing row
                  else:
                      rec = row.getValue('recnum')
                      row.recnum = newValue
                      newValue += 1
                      uCur.updateRow(row)
        else:
          rec = row.getValue('recnum')
          row.recnum = newValue
          newValue += 1
          uCur.updateRow(row)
    del uCur

try:
          infc = r'Database Connections\s14-arcgis-p_OS.sde\PublicWorks.DBO.Sewer_Network\PublicWorks.DBO.ssGravityMain'
          FixDuplicates()

Re: cursor compare last und actual row

UrsRichard — Fri, 11 Sep 2015 08:37:30 GMT

Create! That's exactly what I was lookinf for. Thanks a lot!