Python in field calculator parsing error

Question

I'm trying to perform a selection in an attribute table based on two columns. The intital step I'm intending to perform is to select fields between values, e.g. (a> 0 and a < 10) and from this selection then in the second step find fields in another column, e.g. (if b == 1, return "OK" elif b == 2, return "NOT OK"). I think I'm safe with the logic behind it, but the Python scripting seems to be my drawback. What Am I doing wrong since I get parsing error everytime I try to execute the code?

def Check ( a, b ):
 for (a > 0) and (a < 10):
 if b == 2:
 return "NO"
 elif b == 1:
 return "YES"
 elif b == 0:
 return "MAYBE" 
 for (a => 10) and (a < 15):
 if b == 2:
 return "NO"
 elif b == 1:
 return "YES"
 elif b == 0:
 return "MAYBE"
 for (a > 15):
 if b == 2:
 return "YES"
 elif b == 1:
 return "NO"
 elif b == 0:
 return "MAYBE"

Result (Check)

• Vince: You can use any indent scheme you want, so long as it's four spaces (this has become a defacto standard in Python coding)

Answer 1

Your main problem is the use of "for" instead of "if" with the conditionals related to the first field.

def Check ( a, b ):
 if (a > 0) and (a < 10): #if you don't have negative values, it could be if a<10: . Also, note that you will not return any result for negative values with the present script.
 if b == 2:
 return "NO"
 elif b == 1:
 return "YES"
 elif b == 0:
 return "MAYBE" 
 elif (a => 10) and (a < 15): #elif a<15:
 if b == 2:
 return "NO"
 elif b == 1:
 return "YES"
 elif b == 0:
 return "MAYBE"
 elif (a > 15): #else:
 if b == 2:
 return "YES"
 elif b == 1:
 return "NO"
 elif b == 0:
 return "MAYBE"

Also, make sure that you run it with

Check(!fielda!,!fieldb!)

By the way, in your example the value of "a" doesn't influence the output, so this could be skipped.

• chrkes: Perfect! The use of "for" was the problem. I thought an "if" followed by another "if", looked wrong before I even tried my self, but I learnt something today. Thank you! I'm sure the script can be shortened a lot, but this is simple enough and understandable for a non-pyhton audience.