ArcGIS Pro Calculate Field giving WARNING 002858: Certain rows set to NULL due to error while evaluating Python expression

Question

I'm working with some county level data for the 2016 US Election.

I'm trying to calculate a blank Text field "Winner" based on two numeric fields "votes_dem" and "votes_gop" where it will take the greater of the two values in the numeric fields and input either "Trump" or "Clinton" into the new Winner field.

When I try to run my code block it returns with this warning:

WARNING 002858: Certain rows set to NULL due to error while evaluating Python expression: File "", line 2, in Reclass

I think there's a problem with my syntax, or just the way I'm trying to do it in general (still learning Python)

Wnner = Reclass(!Winner!)

def Reclass(Winner):
    if (votes_gop > votes_dem):
        return Trump
    elif (votes_dem > votes_gop):
        return Clinton

Answer 1

Edited to reflect @Vince's comment which is correct. Firstly, you need to pass the gop and dem votes into the function. Also, you're trying to return a string in your function but haven't enclosed it in quotes.

Try the following:

def Reclass(votes_gop, votes_dem):
    if (votes_gop > votes_dem):
        return "Trump"
    elif (votes_dem > votes_gop):
        return "Clinton"

further, for completeness, you may want to add the case when votes are equal.

def Reclass(votes_gop, votes_dem):
        if (votes_gop > votes_dem):
            return "Trump"
        elif (votes_dem > votes_gop):
            return "Clinton"
        else:
            return "Tie"

Also, this assumes you have valid values for all records in the votes_gop and votes_dem fields. If any of them are Null, you may run into problems.

Also, I just noticed that you're first line has Wnner instead of Winner.

Invocation of the function should be:

Reclass(!votes_gop!,!votes_dem!)