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[BUG] Error: No extension registered which can handle flow when using 'get_flow()' with reinstantiate=True #1626
Description
Details
When trying to use get_flow(1) with reinstantiate=True the following error is raised:
ValueError: No extension registered which can handle flow: 1 (openml.evaluation.EuclideanDistance).
It's the same with all the different flow ids I have tried.
To reproduce
from openml.flows.functions import get_flow
flow = get_flow(1, reinstantiate=True)
Expected Behaviour
Things should work.
Activity
geetu040 commentedon Jan 22, 2026
you can try a different flow from catalogue which uses sklearn, but that will lead to another problem that all the sklearn tagged flows I see there are bounded to version
0.20.xor lessfkiraly commentedon Jan 22, 2026
these are ancient versions.
We have already discussed about decoupling the concept of estimator instansces from versions - but maybe we also should consider this for flows somehow?
EmanAbdelhaleem commentedon Jan 28, 2026
Yup, now I got
ValueError: Trying to deserialize a model with dependency sklearn==0.18.1 not satisfied.What to do then?
geetu040 commentedon Jan 30, 2026
not really a bug, flows depend on library versions, so they expect the setup to have correct versions, does it affect you from running a test? can you tell which test-case exactly troubles you?
Fix get_flow() with reinstantiate=True for flows without extensions
ssudhiravinesh commentedon Mar 7, 2026
Hi @EmanAbdelhaleem !
I've worked on this issue and identified that the error occurs for OpenML-native flows (like evaluation functions) that don't have registered extensions. I've implemented a fix that makes
get_flow()gracefully handle such flows by logging a warning instead of raising an error whenreinstantiate=Trueis passed but no extension is available.The version mismatch issue mentioned in the comments (sklearn==0.18.1 not satisfied) is expected behavior - flows depend on specific library versions. Users can use
strict_version=Falseto work around version mismatches.I'll submit a PR shortly to fix the original issue.