# Script Tester and name 'isNull' is not defined

**URL:** <https://forum.inductiveautomation.com/t/script-tester-and-name-isnull-is-not-defined/8510>\
**Category:** Ignition\
**Created:** [June 3, 2014, 10:29am UTC](https://forum.inductiveautomation.com/t/script-tester-and-name-isnull-is-not-defined/8510 "2014-06-03T10:29:50Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![falko](https://avatars.discourse-cdn.com/v4/letter/f/9de0a6/32.png) [@falko](https://forum.inductiveautomation.com/u/falko)\
**Post date:** [June 3, 2014, 10:29am UTC](https://forum.inductiveautomation.com/t/script-tester-and-name-isnull-is-not-defined/8510/1 "2014-06-03T10:29:50Z")

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Hi!

I have a problem to use isNull() function within Script Tester.  
I am getting error:

Traceback (most recent call last):  
File “”, line 8, in   
NameError: name ‘isNull’ is not defined

What I am thinking is that I have to import some module but I do not have idea which module.  
Is there any manual regarding scripting and modules which has to be import to be able to use certain function?

Thank you

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<div class="post-metadata">

**Author:** ![JordanCClark](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/jordancclark/32/83362_2.png) [@JordanCClark](https://forum.inductiveautomation.com/u/JordanCClark)\
**Post date:** [June 3, 2014, 12:07pm UTC](https://forum.inductiveautomation.com/t/script-tester-and-name-isnull-is-not-defined/8510/2 "2014-06-03T12:07:33Z")

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Hi, falko,

Null in python is None. There are two ways to check for something being None:

`If value is None:
  doSomething
else:
  doSomethingElse
`

`If value == None:
  doSomething
else:
  doSomethingElse
`

Or, to check if it’s not None:

`If value is not None:
  doSomething
else:
  doSomethingElse
`

`If value != None:
  doSomething
else:
  doSomethingElse
`

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<div class="post-metadata">

**Author:** ![falko](https://avatars.discourse-cdn.com/v4/letter/f/9de0a6/32.png) [@falko](https://forum.inductiveautomation.com/u/falko)\
**Post date:** [June 4, 2014, 7:05am UTC](https://forum.inductiveautomation.com/t/script-tester-and-name-isnull-is-not-defined/8510/3 "2014-06-04T07:05:53Z")

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Thanks Jordan,

That is working.  
But still iI have problem with some Expression Functions (Appendix B. Expression Functions from Ignition help). I try to use some of them in Interactive Script Tester, but I am getting similar error, for example:  
NameError: name ‘toradians’ is not defined  
or  
NameError: name ‘toInteger’ is not defined

Question is where I can use them if they are not working in Script Tester?

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<div class="post-metadata">

**Author:** ![JordanCClark](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/jordancclark/32/83362_2.png) [@JordanCClark](https://forum.inductiveautomation.com/u/JordanCClark)\
**Post date:** [June 4, 2014, 10:52am UTC](https://forum.inductiveautomation.com/t/script-tester-and-name-isnull-is-not-defined/8510/4 "2014-06-04T10:52:19Z")

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Ah. Expression language and Scripting are two separate animals.

Expressions are used in Tags and Transaction groups. Scripts are python code.

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<div class="post-metadata">

**Author:** ![falko](https://avatars.discourse-cdn.com/v4/letter/f/9de0a6/32.png) [@falko](https://forum.inductiveautomation.com/u/falko)\
**Post date:** [June 4, 2014, 11:29am UTC](https://forum.inductiveautomation.com/t/script-tester-and-name-isnull-is-not-defined/8510/5 "2014-06-04T11:29:12Z")

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Thanks Jordan,

That was something what I had to know.  
Thanks a lot.