How to write Python if/then statement using information from two fields in field calculator

Question

I am using ArcGIS Desktop 10.6.1. I create a new field of type short integer in the Attribute Table. My new field is named CIPOT and I want to populate it with values from the field CI, but only if values in field Z = 100, otherwise I want CIPOT to equal zero.

My Python script:

def NumValue( CI ):

  if (Z == 100):
    return CI
  else:  return 0

NumValue(!CI! )

Here is a screen shot:

I am getting an error message that global name 'Z' in not defined.

Answer 1

As @NathanW has commented, you have passed the value of your CI field to your function using defNumValue(CI):, but have not passed the value of the Z field.

You can pass the Z value by just adding it to your function variables

def NumValue(CI, Z):
    if (Z == 100):
        return CI
    else:  return 0

Expression:

NumValue(!CI!, !Z!)