topic Re: Calculate Values problems in Python Questions

Calculate Values problems

TimothyElliott — Sun, 26 Jan 2014 21:44:39 GMT

I am trying to write a script to calculate values if there are null values in a table however it never calculates any values and I am pretty sure my code is right.
Where (Operator) is a field with values and null values
and (PointID) is a field with coded values and the Operator name as a 3 letter code stored within the text.

  Expression: Calc (!Operator!)  Code Block: def Calc (Operator):   while (Operator is null):     if (re.search ("DWS", PointID) is TRUE):       return "Don"     elif (re.search ("GMS", PointID) is TRUE):       return "Gordon"     elif (re.search ("JZL", PointID) is TRUE):       return "Julian"     elif (re.search ("AWM", PointID) is TRUE):       return "Anthony"     else return (Operator)

Re: Calculate Values problems

RichardFairhurst — Sat, 11 Dec 2021 18:51:22 GMT

I am trying to write a script to calculate values if there are null values in a table however it never calculates any values and I am pretty sure my code is right.
Where (Operator) is a field with values and null values
and (PointID) is a field with coded values and the Operator name as a 3 letter code stored within the text.
 
Expression:
Calc (!Operator!)

Code Block:
def Calc (Operator):
  while (Operator is null):
    if (re.search ("DWS", PointID) is TRUE):
      return "Don"
    elif (re.search ("GMS", PointID) is TRUE):
      return "Gordon"
    elif (re.search ("JZL", PointID) is TRUE):
      return "Julian"
    elif (re.search ("AWM", PointID) is TRUE):
      return "Anthony"
    else return (Operator)

Your code is not right. You did not feed the PointID into the code block through the expression, so the code block has no idea what PointID means. Your code is wrong for detecting Null values within Python. You don't need a while expression in the field calculator for the records it is calculating, since it iterates all records for the calculated field for you. Finally, your have to return a value for every record calculated, not just Null records, which your code does not do. To succeed the code needs to read:

Expression:
Calc (!Operator!, !PointID!)

Code Block:

def Calc (Operator, PointID):
  if (Operator == None):
    if (re.search ("DWS", PointID) is TRUE):
      return "Don"
    elif (re.search ("GMS", PointID) is TRUE):
      return "Gordon"
    elif (re.search ("JZL", PointID) is TRUE):
      return "Julian"
    elif (re.search ("AWM", PointID) is TRUE):
      return "Anthony"
    else return (Operator)
  else return (Operator)

Re: Calculate Values problems

TimothyElliott — Sat, 11 Dec 2021 18:51:25 GMT

Your code is not right. You did not feed the PointID into the code block through the expression, so the code block has no idea what PointID means. Your code is wrong for detecting Null values within Python. You don't need a while expression in the field calculator for the records it is calculating, since it iterates all records for the calculated field for you. Finally, your have to return a value for every record calculated, not just Null records, which your code does not do. To succeed the code needs to read:

Expression:
Calc (!Operator!, !PointID!)

Code Block:
def Calc (Operator, PointID):
  if (Operator == None):
    if (re.search ("DWS", PointID) is TRUE):
      return "Don"
    elif (re.search ("GMS", PointID) is TRUE):
      return "Gordon"
    elif (re.search ("JZL", PointID) is TRUE):
      return "Julian"
    elif (re.search ("AWM", PointID) is TRUE):
      return "Anthony"
    else return (Operator)
  else return (Operator)

code says there is a syntax problem with line 11, the else statements.

Re: Calculate Values problems

RichardFairhurst — Sat, 11 Dec 2021 18:51:27 GMT

code says there is a syntax problem with line 11, the else statements.

def Calc (Operator, PointID):
  if (Operator == None):
    if (re.search ("DWS", PointID) is TRUE):
      return "Don"
    elif (re.search ("GMS", PointID) is TRUE):
      return "Gordon"
    elif (re.search ("JZL", PointID) is TRUE):
      return "Julian"
    elif (re.search ("AWM", PointID) is TRUE):
      return "Anthony"
    else:
      return (Operator)
  else:
    return (Operator)

Re: Calculate Values problems

TimothyElliott — Sat, 01 Feb 2014 00:22:56 GMT

def Calc (Operator, PointID):   if (Operator == None):     if (re.search ("DWS", PointID) is TRUE):       return "Don"     elif (re.search ("GMS", PointID) is TRUE):       return "Gordon"     elif (re.search ("JZL", PointID) is TRUE):       return "Julian"     elif (re.search ("AWM", PointID) is TRUE):       return "Anthony"     else:       return (Operator)   else:     return (Operator)

I finally got it all to work thanks for pointing me in the right direction all needed to import the re function as its not native in ArcPy and the true statement is not required.

import re def Calc (Operator,PointID):   if (Operator == None):     if (re.search ("AWM",(PointID))):       return "Anthony"     elif (re.search ("AZS",(PointID))):       return "Andrea"     elif (re.search ("ERT",(PointID))):       return "Earl"     else:       return (PointID)   else:     return (Operator)