xcom return_value returns as an item in an array?

[Kyle Nickl <kg...@gmail.com>]

So I run an operator that I name task1. It has an xcom return value. The
value is display as a string as I would expect. But when I go to my next
operator that does an xcom pull the value that gets passed in the in the
value in an array that I see when the operator prints the value like
['my_value] instead of just my_value. I've tried on two different operators
and same thing happens on both each time.

But then whe I tried with a python operator using context inside the code
like context['ti'].xcom_pull(task_ids='task1', key='return_value') the
value is retrieved as expected and not in an array. Which surprised me.

Any ideas on this or how I should properly retrieve this value when I'm
trying to take the return_value and directly pass it in as a parameter
value on another operator?

Example (if the xcom return value is my_value the value the operator gets
is ['my_value']:
retrieveAndDisplayTokenOneWay = TestOperator(
    task_id='task2',
    something="{{ ti.xcom_pull(task_ids=['task1'],key='return_value')}}"

Thanks!

Re: xcom return_value returns as an item in an array?

[Jarek Potiuk <ja...@potiuk.com>]

This happens because you use `task_ids=['tasks1']`

This is how xcom_pull works -you pass there list of tasks - and you get the
list of xcoms as a result. You need to add [0] : "{{
ti.xcom_pull(task_ids=['task1'],key='return_value')[0]}}". or you can also
pass task_id as you did. Both are fine.

XCom_Pull works in three "modes":

* when you pass array - it will return an array of xcoms - one for each
task in the erro-
* when you pass None, it will return array of xcoms from all tasks
* when you pass task_id - it will return the Xcom as a result (no array)

I hope it helps.

J.


On Mon, Aug 16, 2021 at 10:44 PM Kyle Nickl <kg...@gmail.com> wrote:

> So I run an operator that I name task1. It has an xcom return value. The
> value is display as a string as I would expect. But when I go to my next
> operator that does an xcom pull the value that gets passed in the in the
> value in an array that I see when the operator prints the value like
> ['my_value] instead of just my_value. I've tried on two different operators
> and same thing happens on both each time.
>
> But then whe I tried with a python operator using context inside the code
> like context['ti'].xcom_pull(task_ids='task1', key='return_value') the
> value is retrieved as expected and not in an array. Which surprised me.
>
> Any ideas on this or how I should properly retrieve this value when I'm
> trying to take the return_value and directly pass it in as a parameter
> value on another operator?
>
> Example (if the xcom return value is my_value the value the operator gets
> is ['my_value']:
> retrieveAndDisplayTokenOneWay = TestOperator(
>     task_id='task2',
>     something="{{ ti.xcom_pull(task_ids=['task1'],key='return_value')}}"
>
> Thanks!
>
>

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