Calculate repeating values in field

[JeffBaker2]

Anyone have any ideas how to calculate a field so the values (going down the table) are

1

2

3

1

2

3

1

2

3

etc. to the end of the table?

These values will end up being color codes for rendering.  The actual values will be from 0-9, but need some way to get the repeating values in.  Another option might be to calculate random values instead of repeating values.  Any thoughts?

[DanPatterson_Retired]

cnt = 0
def seq_num_max(val):
    global cnt
    if cnt < val:
        cnt += 1
    else:
        cnt = 0
    return cnt

# in expression box ... seq_num_max(3) ... will number from 0 to 3 before repeating‍‍‍‍‍‍‍‍‍‍

will get you started ... for use in the field calculator obviously

[MicahBabinski]

I think this would do it:

In field calculator Codeblock (Python):

def Calculate(repeatingValue):
    interval = 1
    if cntr < 3:
        cntr += interval
    else:
        cntr = 1
    return cntr‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Then in your expression it would be Calculate(!YourFieldName!)

Micah

[DarrenWiens2]

for i in range(10):
    print (i % 3) + 1

1
2
3
1
2
3
1
2
3
1‍‍‍‍‍‍‍‍‍‍‍‍‍

[JeffBaker2]

Thanks for your replies.  Dan, Micah, each of your code pieces seems to run well, but the values are not populating in the highlighted field.  All rows remain Null--see below.  Ideas?

[MicahBabinski]

Hey Jeff,

You'll need to apply that function in the main calc expression box:

seq_num_max(!ColorCode!)

That should do it.

[JeffBaker2]

I am now getting all zero's in the ColorCode field.  Am I setting up the Field Calculator dialog correctly?  Or maybe something else?

[JeffBaker2]

A little more info now . . . 

Each time I run this code:

cnt = 0
def seq_num_max(val):
    global cnt
    if cnt < val:
        cnt += 1
    else:
        cnt = 0
    return cnt

The result calculates ALL values to 0, then to 1, then to 2, then 3, then back to 0 again, and so on.  Still not sure how to get the repeating values?

[DarrenWiens2 · Accepted solution]

This passes the current field value to the function (not what you want - would pass all 0s first time, then all 1s, etc.):

seq_num_max(!ColorCode!)‍‍

Try (you always want 3):

seq_num_max(3)‍‍‍

And code block (untested):

cnt = 0
def seq_num_max(val):
    global cnt
    if cnt < val:
        cnt += 1
    else:
        cnt = 0
    return cnt

Or (untested):

cnt = -1
def seq_num_max(val):
  global cnt
  cnt += 1
  return (cnt % val) + 1‍‍‍‍‍

[JeffBaker2]

And Darren hits the grand slam . . . that worked!  Thank you!

You gave two suggestions--the second one did the trick.  

Thanks to all who shared your ideas.