prefect.futures
¶
Futures represent the execution of a task and allow retrieval of the task run's state.
This module contains the definition for futures as well as utilities for resolving futures in nested data structures.
PrefectFuture
¶
Bases: Generic[R, A]
Represents the result of a computation happening in a task runner.
When tasks are called, they are submitted to a task runner which creates a future for access to the state and result of the task.
Examples:
Define a task that returns a string
>>> from prefect import flow, task
>>> @task
>>> def my_task() -> str:
>>> return "hello"
Calls of this task in a flow will return a future
>>> @flow
>>> def my_flow():
>>> future = my_task.submit() # PrefectFuture[str, Sync] includes result type
>>> future.task_run.id # UUID for the task run
Wait for the task to complete
>>> @flow
>>> def my_flow():
>>> future = my_task.submit()
>>> final_state = future.wait()
Wait N seconds for the task to complete
>>> @flow
>>> def my_flow():
>>> future = my_task.submit()
>>> final_state = future.wait(0.1)
>>> if final_state:
>>> ... # Task done
>>> else:
>>> ... # Task not done yet
Wait for a task to complete and retrieve its result
>>> @flow
>>> def my_flow():
>>> future = my_task.submit()
>>> result = future.result()
>>> assert result == "hello"
Wait N seconds for a task to complete and retrieve its result
>>> @flow
>>> def my_flow():
>>> future = my_task.submit()
>>> result = future.result(timeout=5)
>>> assert result == "hello"
Retrieve the state of a task without waiting for completion
>>> @flow
>>> def my_flow():
>>> future = my_task.submit()
>>> state = future.get_state()
Source code in prefect/futures.py
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get_state
¶
Get the current state of the task run.
Source code in prefect/futures.py
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result
¶
Wait for the run to finish and return the final state.
If the timeout is reached before the run reaches a final state, a TimeoutError
will be raised.
If raise_on_failure
is True
and the task run failed, the task run's
exception will be raised.
Source code in prefect/futures.py
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wait
¶
Wait for the run to finish and return the final state
If the timeout is reached before the run reaches a final state,
None
is returned.
Source code in prefect/futures.py
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call_repr
¶
Generate a repr for a function call as "fn_name(arg_value, kwarg_name=kwarg_value)"
Source code in prefect/futures.py
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resolve_futures_to_data
async
¶
Given a Python built-in collection, recursively find PrefectFutures
and build a
new collection with the same structure with futures resolved to their results.
Resolving futures to their results may wait for execution to complete and require
communication with the API.
Unsupported object types will be returned without modification.
Source code in prefect/futures.py
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resolve_futures_to_states
async
¶
Given a Python built-in collection, recursively find PrefectFutures
and build a
new collection with the same structure with futures resolved to their final states.
Resolving futures to their final states may wait for execution to complete.
Unsupported object types will be returned without modification.
Source code in prefect/futures.py
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