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<@ULVA73B9P> what does this error mean and how do ...
# ask-marvin
a
@Marvin what does this error mean and how do i fix it?
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Encountered exception during execution:
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/prefect/engine.py", line 2169, in orchestrate_task_run
    result = await call.aresult()
             ^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/prefect/_internal/concurrency/calls.py", line 327, in aresult
    return await asyncio.wrap_future(self.future)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/prefect/_internal/concurrency/calls.py", line 352, in _run_sync
    result = self.fn(*self.args, **self.kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/liva/projects/prefect-agent/data-science-main/flows/dbt/tasks.py", line 38, in send_freshness_alert
    webhook = SlackWebhook.load(block_name)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/prefect/utilities/asyncutils.py", line 311, in coroutine_wrapper
    return call()
           ^^^^^^
  File "/usr/local/lib/python3.11/site-packages/prefect/_internal/concurrency/calls.py", line 432, in __call__
    return self.result()
           ^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/prefect/_internal/concurrency/calls.py", line 318, in result
    return self.future.result(timeout=timeout)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/prefect/_internal/concurrency/calls.py", line 179, in result
    return self.__get_result()
           ^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/concurrent/futures/_base.py", line 401, in __get_result
    raise self._exception
  File "/usr/local/lib/python3.11/site-packages/prefect/_internal/concurrency/calls.py", line 389, in _run_async
    result = await coro
             ^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/prefect/client/utilities.py", line 100, in with_injected_client
    return await fn(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/prefect/blocks/core.py", line 844, in load
    return cls._from_block_document(block_document)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/prefect/blocks/core.py", line 642, in _from_block_document
    block = block_cls.parse_obj(block_document.data)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "pydantic/main.py", line 532, in pydantic.main.BaseModel.parse_obj
  File "/usr/local/lib/python3.11/site-packages/prefect/blocks/notifications.py", line 44, in __init__
    apprise.NOTIFY_TYPES += (PREFECT_NOTIFY_TYPE_DEFAULT,)
TypeError: unsupported operand type(s) for +=: 'frozenset' and 'tuple'
m
✅ thought for 268.3 seconds
Short version: Prefect is trying to add its custom notification type to Apprise’s list of types, but in your environment Apprise exposes 
NOTIFY_TYPES
as a frozenset (immutable). That 
+=
on a frozenset causes the TypeError. Why this happens: - Recent Apprise versions (v1.9.4+) introduced breaking changes (e.g., 
NotifyType
became an Enum and 
NOTIFY_TYPES
is immutable). - Older Prefect versions attempted to patch Apprise types at runtime (e.g., 
apprise.NOTIFY_TYPES += (...)
), which now fails. Fixes: - Recommended: Upgrade Prefect to a version that removed this patching and aligned with new Apprise behavior (3.4.14 or newer). - Release notes mention a related fix: Prefect 3.4.14 Release Notes - PR with context: Fix apprise notifications with new Apprise behavior - Alternative: Pin Apprise to a pre-change version (<= 1.9.3). Commands:
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# See what you have installed
python -c "import prefect, apprise; print('prefect:', prefect.__version__, 'apprise:', apprise.__version__)"

# Upgrade Prefect (preferred)
pip install -U prefect

# OR pin Apprise if you cannot upgrade Prefect yet
pip install 'apprise<1.9.4'
Quick test after upgrading:
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from prefect.blocks.notifications import SlackWebhook
SlackWebhook.load("YOUR_BLOCK_NAME").notify("Test from Prefect")
If you share your current versions of Prefect and Apprise, I can confirm the exact path forward.
a
I would like to pin Apprise to 1.9.3. how do i change my pyproject.toml to reflect this ?
@Marvin I would like to pin Apprise to 1.9.3. how do i change my pyproject.toml to reflect this ?
m
✅ thought for 26.2 seconds
Great—pinning Apprise to 1.9.3 is a good workaround. Here are the common pyproject.toml patterns. Pick the one that matches your setup and add/change the Apprise line accordingly. PEP 621 (Hatch, PDM, uv, etc.)
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[project]
name = "your-project"
version = "0.1.0"
dependencies = [
  "prefect>=3.0.0",
  "apprise==1.9.3",
]
Poetry
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[tool.poetry.dependencies]
python = ">=3.11,<3.13"
prefect = "^3.0.0"
apprise = "1.9.3"
After editing, re-lock and install: - Poetry: 
poetry update apprise
(or 
poetry lock && poetry install
) - PDM: 
pdm update apprise
- uv: 
uv add apprise==1.9.3
or 
uv sync
- Pip + build backend: 
pip install -U "apprise==1.9.3"
Verify:
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python -c "import prefect, apprise; print('prefect:', prefect.__version__, 'apprise:', apprise.__version__)"
Context on the issue (if helpful): - Prefect fix: PR 18720 - Release with related notifications fixes: Prefect 3.4.14 If you tell me which tool you’re using (Poetry, PDM, Hatch, uv), I can tailor the exact steps.
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