FIX make scorer.repr work with a partial score_func (scikit-learn#31891)

adrinjalali · web-flow · commit 24844a05117f · 2025-08-11T10:35:55.000+02:00
diff --git a/doc/whats_new/upcoming_changes/sklearn.metrics/31891.fix.rst b/doc/whats_new/upcoming_changes/sklearn.metrics/31891.fix.rst
@@ -0,0 +1,3 @@
+- `repr` on a scorer which has been created with a `partial` `score_func` now correctly
+  works and uses the `repr` of the given `partial` object.
+  By `Adrin Jalali`_.
diff --git a/sklearn/metrics/_scorer.py b/sklearn/metrics/_scorer.py
@@ -102,6 +102,14 @@ def _cached_call(cache, estimator, response_method, *args, **kwargs):
     return result
 
 
+def _get_func_repr_or_name(func):
+    """Returns the name of the function or repr of a partial."""
+    if isinstance(func, partial):
+        return repr(func)
+
+    return func.__name__
+
+
 class _MultimetricScorer:
     """Callable for multimetric scoring used to avoid repeated calls
     to `predict_proba`, `predict`, and `decision_function`.
@@ -262,7 +270,7 @@ def __repr__(self):
         kwargs_string = "".join([f", {k}={v}" for k, v in self._kwargs.items()])
 
         return (
-            f"make_scorer({self._score_func.__name__}{sign_string}"
+            f"make_scorer({_get_func_repr_or_name(self._score_func)}{sign_string}"
             f"{response_method_string}{kwargs_string})"
         )
 
diff --git a/sklearn/metrics/tests/test_score_objects.py b/sklearn/metrics/tests/test_score_objects.py
@@ -1,5 +1,6 @@
 import numbers
 import pickle
+import re
 import warnings
 from copy import deepcopy
 from functools import partial
@@ -218,6 +219,15 @@ def test_all_scorers_repr():
         repr(get_scorer(name))
 
 
+def test_repr_partial():
+    metric = partial(precision_score, pos_label=1)
+    scorer = make_scorer(metric)
+    pattern = (
+        "functools\\.partial\\(<function\\ precision_score\\ at\\ .*>,\\ pos_label=1\\)"
+    )
+    assert re.search(pattern, repr(scorer))
+
+
 def check_scoring_validator_for_single_metric_usecases(scoring_validator):
     # Test all branches of single metric usecases
     estimator = EstimatorWithFitAndScore()

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	+- `repr` on a scorer which has been created with a `partial` `score_func` now correctly
	`2`	+ works and uses the `repr` of the given `partial` object.
	`3`	+ By `Adrin Jalali`_.