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I need help on the Update Cursor function

OLANIYANOLAKUNLE

Im trying to update a field called "GENERATED" with an attribute called "GENERATED" every time i autogenerate a map, i constructed this script and it is not updating and i didnt see an error(s)

rows = arcpy.UpdateCursor("Parcels",'[OBJECTID] = "1"')
row = rows.next()
while row:
    row.setvalue(GENERATED, GENERATED)
    rows.updateRow(row)
    row = rows.next()

Please any suggestions. Im desperate. Thanks

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Accepted answers

ChristopherThompson

I suspect the naming is throwing it off, if GENERATED is the field name, it looks like you're trying to set the value equal to itself. Perhaps this will work:

row.setvalue(GENERATED, 'GENERATED')

That way the function can distinguish between a field and a value.
I've also had success with:

row.GENERATED = 'GENERATED'

All comments

OLANIYANOLAKUNLE

I have issues with dropping my pdf output in the specified destination output folder from my code below, it does create the pdf output though, but never drops it in the specified destination folder

fc = "Parcels"
field = "Block_No"
cursor = arcpy.SearchCursor(fc)
for row in cursor:
    row.getValue(field)
val = row.getValue(field)
field = "Plot_No"
cursor = arcpy.SearchCursor(fc)
for row in cursor:
    row.getValue(field)
val2 = row.getValue(field)
outName = "Block" + str(val) + "Plot_" + str(val2)
outName1 = str(val) + "Plot_" + str(val2) + ".pdf"
arcpy.CreateFolder_management("C:\GIS",outName)
arcpy.mapping.ExportToPDF(mxd,"C:\GIS\outName\outName1)

Any suggestions? Thanks

OLANIYANOLAKUNLE

There are helpful examples in the help for SearchCursor.

2. For a reason i don't know the script
arcpy.MakeFeatureLayer_management("Parcels", "tLyr", '"TDP_Status" = \'GENERATED\'')
count = int(arcpy.GetCount_management("tLyr").getOutput(0))
if count == 0: 
    arcpy.AddMessage("TDP already generated")
else:
    arcpy.Buffer_analysis("Parcels", "ClipFeature", "12.5 meters", "FULL", "ROUND", "LIST")
Continues with the buffer process even if the count is o or 1. Do you know why?

This shouldn't happen if your indents are correct as above. I would test your script by printing a test message (arcpy.AddMessage("Count is: " + str(count)).

The script still continues with the buffer analysis; can you help me with an arcpy script that can end/stop the process if the count condition is true?
Thanks for your information on the pdf naming convention.... I got it. Thanks man Thanks

nimitz

For SAG's (American slang), here's the v10.1 equivalent using the new "data access" update cursor syntax:

OK, for us noobs, what is SAG an acronym for? Screen Actor's Guild? j/k 🙂

curtvprice

1. Please can you shed more light on how to extract the value from your table using a cursor (row.getValue) and the conversion, im still a juvenile with arcpy/python.

There are helpful examples in the help for SearchCursor.

2. For a reason i don't know the script

arcpy.MakeFeatureLayer_management("Parcels", "tLyr", '"TDP_Status" = \'GENERATED\'')
count = int(arcpy.GetCount_management("tLyr").getOutput(0))
if count == 0: 
    arcpy.AddMessage("TDP already generated")
else:
    arcpy.Buffer_analysis("Parcels", "ClipFeature", "12.5 meters", "FULL", "ROUND", "LIST")

Continues with the buffer process even if the count is o or 1. Do you know why?

This shouldn't happen if your indents are correct as above. I would test your script by printing a test message (arcpy.AddMessage("Count is: " + str(count)).

OLANIYANOLAKUNLE

1. Please can you shed more light on how to extract the value from your table using a cursor (row.getValue) and the conversion, im still a juvenile with arcpy/python.

2. For a reason i don't know the script

arcpy.MakeFeatureLayer_management("Parcels", "tLyr", '"TDP_Status" = \'GENERATED\'')
count = int(arcpy.GetCount_management("tLyr").getOutput(0))
if count == 0: 
    arcpy.AddMessage("TDP already generated")
else:
    arcpy.Buffer_analysis("Parcels", "ClipFeature", "12.5 meters", "FULL", "ROUND", "LIST")

Continues with the buffer process even if the count is o or 1. Do you know why?

curtvprice

i want to generate a pdf output by using the arcpy.exporttopdf function, i want the final output to use this nomenclature for naming the pdf output (plot_no.pdf); the plot_no would be derived from an attribute value under the field named plot_no in the attribute table. Please do you have any suggestions.

OK, last post on this thread. 🙂

Extract the value from your table using a cursor (row.getValue), convert it to a string if necessary and construct a pathname to pass to the arcpy.ExportToPDF tool -- like this:

outName = "plot_" + str(val) + ".pdf"

OLANIYANOLAKUNLE

Sorry; I fixed the code above. There's an example for getOutput (I spelled it wrong) in the help for the GetCount tool.

Thanks curtvprice, you've really helped me.

Please can you help me with this?

i want to generate a pdf output by using the arcpy.exporttopdf function, i want the final output to use this nomenclature for naming the pdf output (plot_no.pdf); the plot_no would be derived from an attribute value under the field named plot_no in the attribute table. Please do you have any suggestions.

Thanks

curtvprice

Sorry to bother you again i got this error

Sorry; I fixed the code above. There's an example for getOutput (I spelled it wrong) in the help for the GetCount tool.

OLANIYANOLAKUNLE

Sorry to bother you again i got this error when i tried to run the script after i changed the following

1. arcpy.MakeFeatureLayer("Parcels", "tLyr", '"TDP_Status" = \'GENERATED\'')
MakeFeatureLayer_Management

2. count = int(arcpy.GetCount("tLyr").GetOutput(0))
'GetCount_Management'

 File "<string>", line 1, in <module>
AttributeError: 'Result' object has no attribute 'GetOutput'

Please what do you think

curtvprice

Thanks curtvprice for the nugget of information, please can you help me with this
Please can you kindly help with this script also; i am trying to do a search through my attribute table, for a field called TDP_Status and if the attribute is GENERATED, I want the arcpy script to print TDP ALREADY GENERATED and stop the process else it should continue with the buffer analysis.

Please [post=224499]use [noparse]

 blocks[/noparse][/post] in your posts - it really helps.

No need for a cursor - the GetCount tool is very helpful here.


arcpy.MakeFeatureLayer_management("Parcels", "tLyr", '"TDP_Status" = \'GENERATED\'')
count = int(arcpy.GetCount_management("tLyr").getOutput(0))
if count == 0: 
    arcpy.AddMessage("TDP already generated")
else:
    arcpy.Buffer_analysis("Parcels", "ClipFeature", "12.5 meters", "FULL", "ROUND", "LIST")

OLANIYANOLAKUNLE

Thanks curtvprice for the nugget of information, please can you help me with this
Please can you kindly help with this script also; i am trying to do a search through my attribute table, for a field called TDP_Status and if the attribute is GENERATED, I want the arcpy script to print TDP ALREADY GENERATED and stop the process else it should continue with the buffer analysis. This is my small script

generatedFieldName = "TDP_Status"
rows = arcpy.SearchCursor("Parcels", '"TDP_Status" = \'GENERATED\'')
for row in rows:
if row.TDP_Status = 'GENERATED'
print TDP ALREADY GENERATED
else:
arcpy.Buffer_analysis ("Parcels", "ClipFeature", "12.5 meters", "FULL", "ROUND", "LIST")

Any suggestions?

curtvprice

Where do i add the field?

arcpy.AddField("table","TIME_GEN","TEXT","","",20)
import datetime
now = datetime.datetime.now()
strNow = now.strftime("%d %b %Y %H:%M:%S")
arcpy.CalculateField_management("table","FIXDATE",'"' + strNow + '"')

ChrisSnyder

Don't include the SQL expression in your cursor statement... If your cursor is only returning records where "TDP_Status = 'GENERATED'", how would your else statement ever work... Do you see the issue?

OLANIYANOLAKUNLE

So what do you suggest i do? Please

ChrisSnyder

Since you are only quering records where 'TDP_Status" = 'GENERATED'' in your cursor, the else statment (the Buffer) will never fire off.

OLANIYANOLAKUNLE

curtvprice

Just to debate Curtis' statement about cursors vs. CalculateField...

Thanks Chris - I hope you meant "discuss" -- the "right" way to do something can include many factors, including whether you need to support multiple versions of ArcGIS, what is easiest for you to code/maintain, what you "like", etc....

This is helpful information. I hadn't done any testing and probably didn't notice because like you, I tend to use Calculate Field for simple expressions using VBScript (the default), which as you have said - is faster than python cursors. Great to hear that arcpy.da cursors are near the speed of ArcObjects cursors.

ChrisSnyder

Just to debate Curtis' statement about cursors vs. CalculateField...

In my experience (which may be outdated now), when using the "PYTHON*" option in the CalculateField tool, the performace of the CalculateField tool and the gp/arcpy.UpdateCursor are exactly the same. A post on this topic from four years ago: http://forums.esri.com/Thread.asp?c=93&f=1729&t=262236#806786. In my mind, complex conditional expressions are much easier to deal with in an update cursor, and I generally reserve the CalculateField tool for only very simple expressions.

I have found new arcpy.da cursors are significantly faster (for a number of reasons) and are much more akin to the performace and functionality of the ArcObjects cursors and more similar in performance to the "VB" option in the CalculateField tool.

OLANIYANOLAKUNLE

curtvprice, i intend to include the time in a field called Time_Generated?

import datetime
now = datetime.datetime.now()
strNow = now.strftime("%d %b %Y %H:%M:%S")

Where do i add the field?

curtvprice

doesn't the Calc Field tool simply implement a cursor behind the scenes? Why is that inherently faster? Is it because the cursor doesn't have to work through the interpreter?

I don't know whether Calculate Field uses cursors, but I do know that there are at least three kinds of cursors in the ArcGIS universe: 1. arcpy cursors, 2. ArcObjects cursors (accessed through .NET) and 3. (new at 10.1) arcpy.da cursors.

Calculate Field can do complex decision making with a code block, but can only write to one field. All I know is that CF is much faster and more convenient to code, so for me it's preferable if you only need to write to one field.

curtvprice

how can i include the current time also.

The details are in the Python documentation.

http://docs.python.org/library/time.html

import datetime
now = datetime.datetime.now()
strNow = now.strftime("%d %b %Y %H:%M:%S")

OLANIYANOLAKUNLE

Thanks Curtis Price, but please how can i include the current time also. Thanks

ChristopherThompson

curtvprice;227108 wrote:
Why not get the date as a string and use the Calculate Field tool? This is easier and much faster than a cursor, even the newfangled arcpy.da flavor.

I've often wondered about this, even if you have a series of updates or calculations to make, seems you could easily make a list of those, and iterate through that list. The advantages of a cursor are clear when you have to make decisions about how to handle a particulare feature or row on a case by case basis. But even for simple mass updates like this, doesn't the Calc Field tool simply implement a cursor behind the scenes? Why is that inherently faster? Is it because the cursor doesn't have to work through the interpreter?

curtvprice

myField = "Date_Gener"
>>> rows = arcpy.UpdateCursor("Parcels")
>>> for row in rows:
...    row.setValue(myField,'Date ( )')
...    rows.updateRow(row)
...

Why not get the date as a string and use the Calculate Field tool? This is easier and much faster than a cursor, even the newfangled arcpy.da flavor.

import datetime
Today = str(datetime.date.today())
arcpy.CalculateField_management("Parcels","date_Gener","'" + Today + "'","PYTHON")

This will only calculate the value for selected rows of the layer "Parcels".

OLANIYANOLAKUNLE

Im trying to automatically get the system time and date updated with the update cursor script, this is my script and the error

myField = "Date_Gener"
>>> rows = arcpy.UpdateCursor("Parcels")
>>> for row in rows:
...    row.setValue(myField,'Date ( )')
...    rows.updateRow(row)
...
Runtime error
Traceback (most recent call last):
File "<string>", line 2, in <module>
File "C:\Program Files (x86)\ArcGIS\Desktop10.1\arcpy\arcpy\arcobjects\arcobjects.py", line 1007, in setValue
    return convertArcObjectToPythonObject(self._arc_object.SetValue(*gp_fixargs(args)))
RuntimeError: ERROR 999999: Error executing function.
The value type is incompatible with the field type. [Date_Gener]

Any suggestions? Please....

OLANIYANOLAKUNLE

Thanks all i got it with all your suggestions, what happened was that i had to start an edit session to be able to see the changes. With this i have some layers from a parcel fabric within my dataframe which makes it difficult for me to use the edit = arcpy.da.Editor(workspace) it throws this error - can not open workspace. Any suggestion would go a long way. Thanks

OLANIYANOLAKUNLE

i want to generate a pdf output by using the arcpy.exporttopdf function, i want the final output to use this nomenclature for naming the pdf output (plot_no.pdf); the plot_no would be derived from an attribute value under the field named plot_no in the attribute table. Please do you have any suggestions. Thanks

ChrisSnyder

Only use setValue() if the field name is a variable.

if your field IS NOT a variable:

rows = arcpy.UpdateCursor("Parcels", "FID = 1")
for row in rows:
    row.GENERATED = "GENERATED"
    rows.updateRow(row)

if your field IS a variable:

myField = "GENERATED"
rows = arcpy.UpdateCursor("Parcels", "FID = 1")
for row in rows:
    row.setValue(myField,"GENERATED")
    rows.updateRow(row)

OLANIYANOLAKUNLE

I used your code

Code:
rows = arcpy.UpdateCursor("Parcels", "FID = 1")

for row in rows:
row.setValue("GENERATED", "GENERATED")
rows.updateRow(row)

i did not get any error but the record was not updated? Any suggestions

ChrisSnyder

setvalue vs setValue

Python is case sensitive... Meaning there is a difference between upper case (V) and lower case (v).

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