# system.tag.writeAsync callback Useless?

**URL:** <https://forum.inductiveautomation.com/t/system-tag-writeasync-callback-useless/107665>\
**Category:** Ignition\
**Tags:** ignition81\
**Created:** [June 23, 2025, 9:25am UTC](https://forum.inductiveautomation.com/t/system-tag-writeasync-callback-useless/107665 "2025-06-23T09:25:40Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![taohongyu88](https://avatars.discourse-cdn.com/v4/letter/t/f05b48/32.png) [@taohongyu88](https://forum.inductiveautomation.com/u/taohongyu88)\
**Post date:** [June 23, 2025, 9:25am UTC](https://forum.inductiveautomation.com/t/system-tag-writeasync-callback-useless/107665/1 "2025-06-23T09:25:40Z")

</div>

[system.tag.writeAsync | Ignition User Manual](https://docs.inductiveautomation.com/docs/8.1/appendix/scripting-functions/system-tag/system-tag-writeAsync)

**system.tag.writeBlocking**

```python
returnList2 = system.tag.writeBlocking(['[default]testTag111','[default]testTag22266'],[12,22])
print returnList2
prop = returnList2[0].isGood()
for i in range(len(returnList2)):
	prop=returnList2[i].isGood()
	if(prop==False):
		print 'False'
	else:
		print 'True'

```

![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/8/2/8244e299204f5315c02efcc32d6ebec2753b99f5.png)

Right! Because the second tagPath is not fund.

**system.tag.writeAsync**

```python
def myCallback(asyncReturn):
	for result in asyncReturn:
		if not result.good:
			print 'False'
system.tag.writeAsync(['[default]testTag111','[default]testTag22266'],[12,22],myCallback)

```

I think it should print Flase. Why it print nothing?

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<div class="post-metadata">

**Author:** ![pascal.fragnoud](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pascal.fragnoud/32/24728_2.png) [@pascal.fragnoud](https://forum.inductiveautomation.com/u/pascal.fragnoud)\
**Post date:** [June 23, 2025, 9:48am UTC](https://forum.inductiveautomation.com/t/system-tag-writeasync-callback-useless/107665/2 "2025-06-23T09:48:20Z")

</div>

Because it's printing on another thread.

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<div class="post-metadata">

**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:** [June 23, 2025, 10:50am UTC](https://forum.inductiveautomation.com/t/system-tag-writeasync-callback-useless/107665/3 "2025-06-23T10:50:42Z")

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That's what the callback is for. The whole point of "async" is that the operation occurs separately while the main thread continues with other things. There is nothing to return to the main thread. The callback is later handed the "return" value as its argument.

In the designer script console, only prints from the main thread reach the console.

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<div class="post-metadata">

**Author:** ![taohongyu88](https://avatars.discourse-cdn.com/v4/letter/t/f05b48/32.png) [@taohongyu88](https://forum.inductiveautomation.com/u/taohongyu88)\
**Post date:** [June 23, 2025, 11:13am UTC](https://forum.inductiveautomation.com/t/system-tag-writeasync-callback-useless/107665/4 "2025-06-23T11:13:52Z")

</div>

![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/2/b/2ba744b2a578d01b4f66ddfaca27ef24e519bb20.png)