Using Python in the Field Calculator to select more than one data point

Question

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.

Answer 1

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
    else:
        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.

Answer 2

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]