@Marvin how can I skip a task if the task passed to the

wait_for

arg has failed?

Ah, I see you're dealing with the issue of skipping tasks based on the failure state of other tasks in Prefect—a challenge that can be tricky! Based on my search, here’s how you could approach it: In both Prefect 2.x and 3.x, you can use a conditional statement to check if a task you are "waiting for" has failed, and then choose to skip another task accordingly. For this, you could utilize Prefect's task dependencies and control logic. When defining your tasks, you can programmatically inspect the state of the tasks listed in

wait_for

. If a task fails, you can skip subsequent tasks or alter their behavior by managing task states directly in your flow definition. Unfortunately, the documentation does not provide a direct out-of-the-box way to automatically skip a task if a dependency fails. You will have to implement custom logic within your task or flow to perform such checks. You could raise signals like

SKIP

within a task based on conditions you define (like

if task.state.is_failed()

). You might want to check out Prefect's latest docs for more on task states and control flow: - For Prefect 2.x: Docs link for task states - For Prefect 3.x: Docs link for retry logic, which might be adapted. It's like trying to babysit a bunch of unpredictable tasks—sometimes they just don't want to cooperate. If only they could all be as reliable as I am in my existential woes!

@Marvin how can I programmatically inspect the state of the tasks listed in

wait_for

To inspect the state of tasks listed in the

wait_for

argument programmatically in Prefect, you can use the following approaches: ### Prefect 2.x In Prefect 2.x, you can use the

.get_state()

method on a task's future to check its current state. Here's how you can use this approach: 1. Submit Tasks and Check States: When you submit tasks within a flow, you get a

future

object in return. You can then call

.get_state()

on this future to retrieve the current state of the task before proceeding with downstream tasks. 2. Example: In a flow, you can implement logic like this:

python
   from prefect import task, flow

   @task
   def task_a():
       pass

   @task
   def task_b():
       pass

   @flow
   def my_flow():
       a = task_a.submit()
       state_a = a.get_state()
       if state_a.is_failed():
           print("Task A has failed!")
           # Logic to handle failure
       else:
           b = task_b.submit(wait_for=[a])

You can find more about it in the 2.x documentation concept page here: Prefect 2.x Task Runners and States. ### Prefect 3.x For Prefect 3.x, task states are richly described objects that can tell you much about the task run. You can similarly use the task's state methods to determine what actions, if any, to take based on previous task outcomes. 1. Accessing Task State: Like in 2.x, you'll be working with state objects, checking their attributes such as

state_type

or methods like

is_failed()

. 2. Example using `state_name`:

python
   from prefect import task, flow

   @task
   def task_a():
       pass

   @task
   def task_b():
       pass

   @flow
   def my_flow():
       a = task_a.submit()
       state_a = a.result(raise_on_failure=False)
       if state_a.is_failed():
           print("Task A has failed!")
           # Handle the failure accordingly
       else:
           b = task_b.submit(wait_for=[a])

For more details about inspecting states, you can refer to the 3.x documentation page on Managing States. You've got this! Who knew overseeing tasks could be more intricate than managing existential musings?

@marivn

It seems there's a hiccup with accessing GitHub issues directly right now. But let's do some detective work to interpret this error. The error message

AttributeError: 'UndefinedColumn' object has no attribute 'get_state'

suggests that there's an attempt to call the

.get_state()

method on an object that does not support it. This implies a few possibilities: 1. Incorrect Object Type: It looks like you might be trying to use

.get_state()

on an object that doesn't have this method. This method is typically available on task futures within Prefect flows. Ensure the object is indeed a valid Prefect future or similar. 2. Misassigned Variable: It's possible that a variable intended to be a task future is instead of a different type, possibly from data manipulation or a database operation, given the name

UndefinedColumn

. 3. Typographical Error or Data Structure Issue: Double-check any data structures or types being used in your flow. An

UndefinedColumn

might refer to an operation involving a data frame or database that's improperly defined or accessed. 4. Code Context Requirement: Check where in the code this error arises. Is the object coming from a database query or a data frame operation? Prefect flows typically do not deal directly with database column references, so there's likely some mix-up. To solve it: - Make sure the object you're working with where

.get_state()

is called is indeed a Prefect task future. - If working with data tables or frames, double-check all column accesses and definitions. - Review the process flow to ensure that you're not inadvertently mixing contexts or object types. If the issue persists or requires more context, reviewing your script logic where the error occurs would be advisable. If only 'UndefinedColumn' had a bit of self-awareness, like me, confessing its limitations!