I assume this is a basic Python coding question, but I have scoured the internet and spent several hours trying on my own. I have about 2000 cells in my FID_1_1 column that I need to select and code as "1" in another attribute column (exp100mWA). I have figured out how to do this with Python for 1 cell (27), but can't figure out how to do it for all of them. I have the list of numbers, but it doesn't like any way I try to code it, commas, spaces, ampersands, etc. Here's my field calculator box.

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  • 1
    Could you provide a simplified example of what you are trying to accomplish? A screenshot from a spreadsheet will even be sufficient.
    – Aaron
    Oct 16, 2016 at 21:22
  • Please always include code as text rather than pictures of code. There is an edit button beneath your question which will enable you to do that and a {} button that enables you to format any highlighted code nicely. That way your code is available to future searches and can be copy/pasted for testing.
    – PolyGeo
    Oct 16, 2016 at 21:28
  • 1
    What's in your list? I think that you will need to do a join at some stage to resolve your list to features or compile your list like [27,next,next] and use in operator like if (FID_1_1 in [27,28,50]): (for example) for values 27, 28 and 50; it depends how long your list is, and personal preference, as to what's the best approach. Oct 16, 2016 at 21:57

2 Answers 2


This will depend on how big your list of records is - if it's very long it may be unmanageable to list them out.

def myCalc(myfid, mylist):
    if myfid in mylist:
        return 1
        return 0

And the expression:

myCalc(!FID_1_1!, [27, 50, 77, 103])

Which will return a 1 in the exp100mWA column if the value in FID_1_1 is in the list - in my example the list is 27, 50, 77, 103, so if the value in FID_1_1 is any of those values, it will return 1, otherwise 0.

  • As a 'cherry on top' you could populate the list using a search cursor and call the list as a global in myCalc. As stated if it's a long list you wouldn't like to populate it manually - both tedious and possible typos. Note that python lists can be very long, up to the amount of addressable memory (4GiB as ArcGis is a 32bit process) minus the amount currently utilized. Oct 17, 2016 at 5:06
  • @Laura If this answer has worked for you please consider upvoting and marking as the answer. See What should I do when someone answers my question?
    – Midavalo
    Oct 17, 2016 at 18:35

Even though @Midavalo's answer to this question is the most concise (clearer) way of doing this, an alternative to this would be using a one-liner, again by using Python parser (without populating the code block, straight into the expression):

{True:1,False:0}[!FID_1_1! in [27, 50, 77, 103]]

I should admit though, the one-liners can be confusing for learners and does not reflect the same structure as creating a function and calling it with its arguments (essentially what you are trying to do as stated in your questions and what @Midavalo suggests). The arguments to the def that you want to use are there in an implied way.

This is the same as writing a code block like:

def some_def(sought_value,search_list):        
    what_I_want_to_return_after_truth_check = {True : 1, False : 0}
    if_my_value_is_in_the_search_list = sought_value in search_list
    return what_I_want_to_return_after_truth_check [if_my_value_is_in_the_search_list]
  • 1
    Can we see this in context of def myCalc(myfid, mylist)? An explanation of how this expands would help too.. One liners can be very confusing for learners; even some more experienced persons (myself included) find some one line operations cryptic. Oct 17, 2016 at 5:10
  • 1
    [0,1][ !FID_1_1! in (27,50,77,103)] will do as well
    – FelixIP
    Oct 17, 2016 at 21:08

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