Generate Random Number in Global Tag

Ignition
,
1

Is there a simple way to generate a random number in a global tag, so that the tag can run by itself and generate random numbers for itself?

Initial Attempt:

  • Global script with function to generate random number
  • Call global script in runScript in expression
2

In an expression tag, runScript("import random; random.randint(0, 1000)", 0) should work.

3

I am using the free and latest version of Ignition.

I tried that originally, but I get an error:

Error evaluating tag: Error parsing script for runScript() expression: SyntaxError: ("no viable alternative at input '='", ('expression:runScript', 1, 9, '__RESULT = import random; random.randint(0, 1000)\n'))

4

Ah, yeah, looks like the single line import syntax won’t work. Make a shared script, with a single defined function:

import random
	
def randint(lower, upper):
	return random.randint(lower, upper)

Then call it from your expression tag:
runScript("shared.agg.randint", 0, 0, 1000)

5

Thanks for the suggestion.

My bad that I didn’t mention that was my initial attempt. I update my question above.

I was hoping for something cleaner than this.

6

The trouble you are experiencing is due to the fact that runScript() is prefixing the string you feed it with an assignment statement to a hidden variable. So the code that actually executes in Paul’s first suggestion looks like this:

__someVar = import random; random.randint(0, 1000)

And then the __someVar value is fished out of the local variable table to feed to the binding. Not valid python.

If you add a real newline to your string expression, you can print dir() to see what that variable name is. You can also assign a constant temporarily, with a newline, import, execute anything, and assign a real return value several lines later.

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7

I am a little lost with what you are saying…could you please give an example?

8

Use Paul’s second suggestion.

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