Field Calculator: Simple Python If-then and maths

Question

I want to take all positive values in a field and multiply them by -1000. To do this, I put together the following code block:

def myCalc(x):
 if (x > 0):
 x*(-1000)
 return x
 else:
 return x

and then I call the expression:

myCalc( !FieldName! )

However, when I execute this field calculation, I get no warnings or errors, but the values in my field also don't change. The numbers look like this (before and after the calculation):

enter image description here

What is wrong with my code?

Answer 1

You need to reassign x to your calculation:

def myCalc(x):
 if (x > 0):
 x = x*(-1000)
 return x
 else:
 return x

If you'd like to save some typing you can simplify your logic a little:

def myCalc(x):
 if (x > 0):
 x = x*(-1000)
 return x

• Stella: Thanks! It's been a while since I had to do logic like this. It's always the little things that I miss. :D