# Trouble using runScript **URL:** \ **Category:** Ignition\ **Created:** [March 28, 2017, 8:02pm UTC](https://forum.inductiveautomation.com/t/trouble-using-runscript/12854 "2017-03-28T20:02:35Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![waker1der](https://avatars.discourse-cdn.com/v4/letter/w/dbc845/32.png) [@waker1der](https://forum.inductiveautomation.com/u/waker1der)\ **Post date:** [March 28, 2017, 8:02pm UTC](https://forum.inductiveautomation.com/t/trouble-using-runscript/12854/1 "2017-03-28T20:02:35Z")
Hi I am trying to use runScript in an expression tag that is part of a UDT. the UDT has 3 query tags that pull values from my DB. All values are int. I want to work out rate of change between two of the values using a script so if the rate is negative I can handle the value. my project script called rateOfChange is as follows. `def getChange(current, previous): if current == previous: return 100.0 change = current - previous try: percentage_change = (change / float(old_value)) if multiply: percentage_change = percentage_change * 100 return percentage_change except ZeroDivisionError: return None` then in my expression tag I have added the following ```auto runScript("project.rateOfChange.get_change({[.]5min},{[.]10min})",150000) ``` so the inputs in to my function are the tag values for 5min and 10min tags. I have also tried this without the “” but I get the following error `Last Error Cause com.inductiveautomation.ignition.common.expressions.ExpressionException: Error parsing script for runScript() expression: SyntaxError: ("no viable alternative at input '.'", ('', 1, 44, '__RESULT = project.rateOfChange.getChange({[.]5min},{[.]10min})\n')) ERROR\n')) ERROR` can anyone help? ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [March 28, 2017, 8:17pm UTC](https://forum.inductiveautomation.com/t/trouble-using-runscript/12854/2 "2017-03-28T20:17:29Z")
Three changes are needed: 1. You must construct a string for runScript()'s first parameter that is valid python by itself. 2. You cannot use project.\* scripts in expression tags, other than client tags. You’ll have to put the function you need in the shared.\* scripts. 3. Expression tags run at their scan class. The “15000” would have been ignored. Something like this:`runScript("shared.rateOfChange.get_change("+{[.]5min}+","+{[.]10min}+")")` ---
**Author:** ![waker1der](https://avatars.discourse-cdn.com/v4/letter/w/dbc845/32.png) [@waker1der](https://forum.inductiveautomation.com/u/waker1der)\ **Post date:** [March 29, 2017, 7:52am UTC](https://forum.inductiveautomation.com/t/trouble-using-runscript/12854/3 "2017-03-29T07:52:27Z")
thank you, i didn’t realise I had to build the string like that. and yes my script was jargon 😊 all works now, thank you for the help ---
**Author:** ![waker1der](https://avatars.discourse-cdn.com/v4/letter/w/dbc845/32.png) [@waker1der](https://forum.inductiveautomation.com/u/waker1der)\ **Post date:** [March 29, 2017, 8:15am UTC](https://forum.inductiveautomation.com/t/trouble-using-runscript/12854/4 "2017-03-29T08:15:41Z")
for anyone interested i wrote the following for my rate of change script ```auto def getChange(x1,y1,x2,y2): if y1 == y2: return 0 else: try: rate = (float(y2-y1)/float(x2-x1)) return rate except ZeroDivisionError: return 0 ``` ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [March 29, 2017, 1:44pm UTC](https://forum.inductiveautomation.com/t/trouble-using-runscript/12854/5 "2017-03-29T13:44:39Z")
I noticed you posted in the v7.7 forum, so I didn’t mention the [new features of runScript](https://inductiveautomation.com/downloads/changelog/410) available in v7.8. But you might consider using [objectScript()](https://www.automation-pros.com/simaids/doc/expression.objectscript.html) instead, from the [Simulation Aids](https://inductiveautomation.com/moduleshowcase/module/automation-professionals-llc-simulation-aids) module, if you need more flexibility. ---
**Author:** ![jose.granero](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/jose.granero/32/11190_2.png) [@jose.granero](https://forum.inductiveautomation.com/u/jose.granero)\ **Post date:** [September 15, 2017, 10:55am UTC](https://forum.inductiveautomation.com/t/trouble-using-runscript/12854/6 "2017-09-15T10:55:48Z")
Hi Phil, I’ve tried to use runScript in an expression tag part of a UDT also contained in another UDT but haven’t been able to make it work. I’ve even simplified the script so that it just returned a UDT tag with the same result. Any ideas will be welcome. I’m usind V9.3 ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [September 15, 2017, 12:34pm UTC](https://forum.inductiveautomation.com/t/trouble-using-runscript/12854/7 "2017-09-15T12:34:18Z")
> [@jose.granero](#): > > ... but haven't been able to make it work. I wouldn't expect runScript to be much help in tag expressions. objectScript() might be more helpful, but you'll have to share the details. I only use UDTs to automate tag construction, not in bindings or expressions, so I'm not sure what underlying java types would be needed to return a UDT from a script expression. ---
**Author:** ![snoopyflyingace](https://avatars.discourse-cdn.com/v4/letter/s/bcef8e/32.png) [@snoopyflyingace](https://forum.inductiveautomation.com/u/snoopyflyingace)\ **Post date:** [October 17, 2017, 10:49pm UTC](https://forum.inductiveautomation.com/t/trouble-using-runscript/12854/8 "2017-10-17T22:49:22Z")
How do you setup alarming for rate of change?