topic Re: Field calculation for loop incremented by 1 in Data Management Questions

Field calculation for loop incremented by 1

KimballHansen — Tue, 04 Oct 2011 14:49:38 GMT

Hi,

I have my attribute table sorted ascending according to my street names (Aprox. 1914 records). I need to make a new field that starts at 10,000 and increments by 1 until it is filled. Is there a way I can do this? I'm thinking of doing some loop that increments by one (because the default for loop in the field calculator repeats the same number) but I don't know how to do that. Any help? Thanks.

Kimball Hansen

Re: Field calculation for loop incremented by 1

TerrySilveus — Sun, 12 Dec 2021 06:58:33 GMT

Hi,

I have my attribute table sorted ascending according to my street names (Aprox. 1914 records). I need to make a new field that starts at 10,000 and increments by 1 until it is filled. Is there a way I can do this? I'm thinking of doing some loop that increments by one (because the default for loop in the field calculator repeats the same number) but I don't know how to do that. Any help? Thanks.

Kimball Hansen

Not sure how you would do it in the field calculator, but you could create a script

    updateTheRows = arcpy.UpdateCursor("C:\\Filename.shp","","","","AddressName A" ) #get the rows from the shapefile order by address ascending
    i = 0    
    for updateTheRow in updateTheRows:
        updateTheRow.setValue("FieldNameToUpdate",10000 + i)
        updateTheRows.updateRow(updateTheRow)
        i= i+1

    del updateTheRow
    del updateTheRows

Re: Field calculation for loop incremented by 1

KimballHansen — Wed, 05 Oct 2011 17:16:10 GMT

Thanks. I'm very new to python and scripts and don't understand how to begin with that code. Could you please give me a step by step example? Also, which variables are yours that I'm going to cut so I can paste mine?

Kimball Hansen

Re: Field calculation for loop incremented by 1

TomMagdaleno — Wed, 05 Oct 2011 20:12:27 GMT

Hi Kimball I know how you feel about being new to python.
Go into your table, right click on the field you want to populate and go to field calculator. Click the Python button on the top (default is VB). Paste the code into the field calculator. TPalmer already changed pStart to 10000 for you, but you can change that number to whatever starting number you need.

rec=0
def autoIncrement():
global rec
pStart = 10000 #adjust start value, if req'd
pInterval = 1 #adjust interval value, if req'd
if (rec == 0):
rec = pStart
else:
rec = rec + pInterval
return rec
__esri_field_calculator_splitter__
autoIncrement().

Re: Field calculation for loop incremented by 1

KimballHansen — Wed, 05 Oct 2011 21:38:22 GMT

I copied that code and when I run the Field Calculator I get an error. The error number is 000539 if that has any relevance to you. Does the field have to be a certain type? (I tried int and double and both didn't work). Or do all the records need to have zero or 1 first in them to us the code? I don't have any other guesses of what to do.

Re: Field calculation for loop incremented by 1

TerrySilveus — Thu, 06 Oct 2011 18:18:58 GMT

I copied that code and when I run the Field Calculator I get an error. The error number is 000539 if that has any relevance to you. Does the field have to be a certain type? (I tried int and double and both didn't work). Or do all the records need to have zero or 1 first in them to us the code? I don't have any other guesses of what to do.

There should have been a text message after the number, the text will be more useful to determine the issue, however make sure your indenting is correct for python and that Python is checked as the code type. Python REQUIRES block indenting

However, I don't believe this code takes into account that you wanted the records numbered in address order.

Re: Field calculation for loop incremented by 1

KimballHansen — Thu, 06 Oct 2011 20:06:38 GMT

There should have been a text message after the number, the text will be more useful to determine the issue, however make sure your indenting is correct for python and that Python is checked as the code type. Python REQUIRES block indenting

However, I don't believe this code takes into account that you wanted the records numbered in address order.

I don't know Python so I don't know what parts to indent.

Re: Field calculation for loop incremented by 1

TerrySilveus — Sun, 12 Dec 2021 06:58:36 GMT

I don't know Python so I don't know what parts to indent.

rec=0
def autoIncrement():
   global rec
   pStart = 10000 #adjust start value, if req'd
   pInterval = 1 #adjust interval value, if req'd
   if (rec == 0):
      rec = pStart
   else:
      rec = rec + pInterval
   return rec

You should check that you have "use code block" checked and "python" selected
then autoIncrement() goes in the bottom section and the function above goes in the top section "the code block"

Re: Field calculation for loop incremented by 1

JeffWard — Sun, 12 Dec 2021 06:58:38 GMT

Right click on the field and choose "Field Calculator", select the Python radio button at the top and make sure the Show Codeblock box is checked. Then select and copy lines of code in the first code block below and put them in the Pre-Logic Script Code block.

rec=0 def autoIncrement():
    global rec
    pStart = 10000 #adjust start value, if req'd
    pInterval = 1 #adjust interval value, if req'd
    if (rec == 0):
       rec = pStart
    else:
       rec = rec + pInterval
    return rec

If you copy from the above code block, it should keep the proper indentation.

Then select and copy the below code and paste it into the box below YOURFIELDNAME =

autoIncrement()

That should run and get you the results you need. If not, you probably are trying to put a number in a text field or something.

I have attached a screen capture of what my field calculator dialog looks like.

Re: Field calculation for loop incremented by 1

JeffWard — Fri, 07 Oct 2011 19:57:38 GMT

Also make sure that you have 0 records selected or the field calculator will only calculate values for the selected records. I can't tell you how many times I have put in a script and had it run without any errors but it didn't look like any of the field values were changed. They were changed, just the values for the selected records.

Re: Field calculation for loop incremented by 1

KimballHansen — Fri, 07 Oct 2011 21:20:56 GMT

That worked perfectly. Thanks Jeff. When I ran it however it listed the numbers in order according to the OBJECTID field. I would like to have it run the calculator when I sort a different field ascending. I want to list my streets in alphabetical order and create this new field and run the script so the numbers ascend according to the aphabetical streets. Do you know if it's possible to do that or does it always sort according to the OBJECTID field?

Re: Field calculation for loop incremented by 1

TerrySilveus — Fri, 07 Oct 2011 21:29:35 GMT

That worked perfectly. Thanks Jeff. When I ran it however it listed the numbers in order according to the OBJECTID field. I would like to have it run the calculator when I sort a different field ascending. I want to list my streets in alphabetical order and create this new field and run the script so the numbers ascend according to the aphabetical streets. Do you know if it's possible to do that or does it always sort according to the OBJECTID field?

That's what I suggested would happen in a previous post. If you give my code a try as a python script you will be able to set any order you want. I just am not sure how to translate that to the field calculator, because I don't use the field calculator that much.

Re: Field calculation for loop incremented by 1

Anonymous User — Thu, 25 Feb 2016 18:04:07 GMT

I know this is an old thread, but how does it know to loop through the rows? I've seen this bit of code posted elsewhere and I never understood why just a for loop wouldn't work.

Re: Field calculation for loop incremented by 1

DanPatterson_Retired — Thu, 25 Feb 2016 18:54:51 GMT

In short....that is what the field calculator does... it provides the framework to loop through the rows and apply a function, which is also why it works on selections leaving the unselected untouched. This would require a separate bit of code in itself to work with selections. It does have its drawbacks, like having to use globals to keep track of what has gone on in the previous row (ie a previous value).

Sometimes the field calculator is just faster for simple things. It only gets difficult when people try to push the envelop and get it to do things for which it wasn't designed.