topic Re: Python code to subtract a value but don't go below 0 in ArcGIS Pro Questions

Python code to subtract a value but don't go below 0

FlightDeck — Thu, 11 Jan 2024 20:02:20 GMT

I need to subtract a value from a field and return that value to the new field, but if the value is below 0 simply return 0. I know I can do this with calculate field but I am unsure of how to write this in Python.

Example:

3200-1200=2000

800-1200=0

1211-1200=11

80-1200=0

Thanks for any help.

Re: Python code to subtract a value but don't go below 0

DavidSolari — Thu, 11 Jan 2024 20:50:56 GMT

As a one-line function:

def sub_to_zero(a, b): return a - b if a > b else 0

Re: Python code to subtract a value but don't go below 0

rwrenner_esri — Thu, 11 Jan 2024 21:01:39 GMT

David just beat me to posting with a very concise option, but here's a multiline option which does the same thing (this part goes in the code block):

def fancy_subtract(subtract_from): value = 1200 #define value here if subtract_from < value: return 0 else: diff = subtract_from - value return diff

In a field calculation, you can use this by calling the function on your field:

fancy_subtract(!field_name!)

Re: Python code to subtract a value but don't go below 0

clt_cabq — Thu, 11 Jan 2024 21:00:33 GMT

There is probably a more elegant or 'pythonic' way to do this but this will do what you want I think:

def calc_sub(num1, num2): out = num1-num2 if out < 0: ret_val = 0 else: ret_val = out return ret_val #test using the following: x = 10 y = 8 print(calc_sub(x,y))#should return 2 print(calc_sub(y,x))#should return 0

Re: Python code to subtract a value but don't go below 0

RhettZufelt — Thu, 11 Jan 2024 21:04:32 GMT

can use the max() function.

Takes the max value. Since 0 is larger than any negative number, will return 0