Script to return multiple missing values based on other criteria

Question

I have a field, CHPROPSC, that I would like to code with missings as -97, -98 or -99 and a calculated value based on the value of field PRCHSCH04 and PRCHSCH13. Essentially, if the value in PRCHSCH04 is -99 only then CHPROPSC = -98. If the value in PRCHSCH13 is -99 only then CHPROPSC = -97. If the value in both is -99 then CHPROPSC = -99. Otherwise CHPROPSC = PRCHSCH13 - PRCHSCH04. I tried this Python script (and a few variations of this) without the codeblock but there was a processing failure: -97 if !PRCHSCH13! == -99 & !PRCHSCH04! <> -99 -98 elif !PRCHSCH13! <> -99 & !PRCHSCH04! == -99 -99 elif !PRCHSCH13! == -99 & !PRCHSCH04! == -99 else float( !PRCHSCH13! )- !PRCHSCH04! I am sure my syntax with the elif is the most likely problem. Any advice as to where the error is here? Thanks, Steve

DanPatterson_Retired · Answer

Example now provide for both a conventional and list comprehension and generator expression.

DanPatterson_Retired · Answer

Other thoughts pretend you have two lists fld_0 = [-99,-99,-98,10] fld_1 = [-98,-99,-99,5] and you want to use a function. I didn't like your -99,-98, ans = [ -98-(a-b) for a,b in zip(fld_0, fld_1)] returns >>> ans [-97, -98, -99, -103] Don't like the -103 this works conceptually like in python script below except for the last case which means you would need to fix the expression like ans = [( -98 - (a-b)) if (a-b) <= 1 else (a-b) for a,b in zip(fld_0,fld_1)] or in stacked list comprehension form... ans = [ ( -98 - (a-b)) # do this if (a-b) <= 1 # if this else (a-b) # else this for a,b in zip(fld_0,fld_1)] # using these I will think on the options some more. a,b = ans: -99,-98=-97 a,b = ans: -99,-99=-99 a,b = ans: -98,-99=-98 a,b = ans: 10,5=5.0 # ---- The field calculator ---- as a code block it would look like this # code block def func(a,b): if (a == -99): if (b <> -99): ans = -97 else: ans = -99 else: if (b == -99): ans = -98 else: ans = float(a) - b return ans # expression box func(( !Fld_0!, !Fld_1!) ‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ as a list comprehension expression you still have to use a code block since the field calculator doesn't support iterable objects etc. You can also use a generator like in the second example # code block def LC_func(a,b): return [ ( -98 - (a-b)) if ((a-b) <= 1) else (a-b) ][0] # expression box LC_func( !Fld_0!, !Fld_1!) #OR def LC_func2(a,b): return ( ( -98 - (a-b)) if ((a-b) <= 1) else (a-b) ) # expression box LC_func2( !Fld_0!, !Fld_1!) ‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ now the extra [0] is because a list comprehension returns a list, and since you are working with only 2 fields and one output value, you only need to get the first one. EDIT----------- Totally untried, since I am on an iThing with Arc* It has been tried THE FINE PRINT in the above example, it is assumed that ... a - b .... does not produce values in the range -1 to 1 inclusive... If this is a possibility, then the reclass values will need to be changed... think about it. EDIT updated expression to account for -97, -99 combination Code block def LC_func2(a,b): return ( (a+abs(a-b)) if ((a-b)<=1) else min(a,(a-b)) ) Expression box LC_func2( !Fld_0!, !Fld_1!)

DarrenWiens2 · Answer

Try: -97 if !PRCHSCH13! == -99 and !PRCHSCH04! <> -99 else -98 if !PRCHSCH13! <> -99 and !PRCHSCH04! == -99 else -99 if !PRCHSCH13! == -99 and !PRCHSCH04! == -99 else float( !PRCHSCH13! ) - !PRCHSCH04! I'll just say this type of thing is somewhat frowned upon as being difficult to read.