Hi I m receiving this error when trying to use `upstream tas

Question

Hi I m receiving this error when trying to use `upstream tasks` Does someone know what I m doing wrong My intention is to execute `task 3` only after `task 1` and `task 2`is finished since it depends on the output of them and start `task 4` only after the `task 3` is finished How can I accomplish that Code and output error in thread

William Jamir · Answer

```from prefect import Flow task unmapped task def task 1 return 1 2 task def task 2 return 2 task def task 3 parameter1 parameter2 if parameter1 + parameter2 gt = 50 raise ValueError Value is too high task def task 4 parameter1 parameter2 print parameter1 parameter2 with Flow name= a as flow p1 = task 1 p2 = task 2 task 3 map parameter1=p1 parameter2=unmapped p2 task 4 p1 p2 upstream tasks= task 3 flow run ```

William Jamir · Answer

``` 2022 06 18 09 38 54+0200 INFO prefect FlowRunner | Beginning Flow run for a 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 1 Starting task run 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 1 Finished task run for task with final state Success 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 2 Starting task run 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 2 Finished task run for task with final state Success 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 3 Starting task run 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 3 Finished task run for task with final state Mapped 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 3 0 Starting task run 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 3 0 Finished task run for task with final state Success 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 3 1 Starting task run 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 3 1 Finished task run for task with final state Success 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 3 Starting task run 2022 06 18 09 38 54+0200 ERROR prefect TaskRunner | Task task 3 Exception encountered during task execution Traceback most recent call last File Users william pyenv versions myenv lib python3 9 site packages prefect engine task runner py line 880 in get task run state value = prefect utilities executors run task with timeout File Users william pyenv versions emyenv lib python3 9 site packages prefect utilities executors py line 468 in run task with timeout return task run args kwargs type ignore TypeError task 3 missing 2 required positional arguments parameter1 and parameter2 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 3 Finished task run for task with final state Failed 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 4 Starting task run 2022 06 18 09 38 54+0200 INFO prefect TaskRunner | Task task 4 Finished task run for task with final state TriggerFailed 2022 06 18 09 38 54+0200 INFO prefect FlowRunner | Flow run FAILED some reference tasks failed Process finished with exit code 0```

Anna Geller · Answer

Try assigning task3 map to a variable e g t3 and pass t3 as upstream tasks

Kevin Kho · Answer

I think it s ```with Flow name= a as flow p1 = task 1 p2 = task 2 a = task 3 map parameter1=p1 parameter2=unmapped p2 task 4 p1 p2 upstream tasks= unmapped a ``` like Anna suggested

William Jamir · Answer

Thanks Kevin and Anna I see know my issue I dont know why I thought that the correct approach would be to refer directly to the decorated function