Remove deprecated k= argument alias from Top-N metrics

docs/guide/evaluation/rankings.rst

@@ -15,11 +15,17 @@ list and a test rating list, both as :py:class:`item lists
 <lenskit.data.ItemList>`; most metrics require the recommendation item list to
 be :py:attr:`~lenskit.data.ItemList.ordered`.
 
-All LensKit ranking metrics take `k` as a constructor argument to control the
+All LensKit ranking metrics take ``n`` as a constructor argument to control the
 list of the length that is considered; this allows multiple measurements (e.g.
 HR@5 and HR@10) to be computed from a single set of rankings.
 
+.. versionchanged:: 2026.1
+
+    The argument for the list length has changed from ``k`` to ``n``, for
+    consistency across LensKit.
+
 .. versionchanged:: 2025.1
+
     The top-N accuracy metric interface has changed to use item lists, and to
     be simpler to implement.
 

docs/releases/2026.rst

@@ -74,6 +74,8 @@ Breaking Changes
   (:pr:`1052`).
 - Removed the ``n`` option to :func:`~lenskit.pipeline.predict_pipeline`
   (:issue:`835`).
+- Removed the deprecated ``k=`` alias for the ``n=`` option in ranking metrics
+  (:issue:`889`, :pr:`1073`).
 - Removed the deprecated unrated and all-items candidate selectors, in favor of
   :class:`~lenskit.basic.TrainingItemsCandidateSelector` (:issue:`935`).
 

src/lenskit/metrics/ranking/_base.py

@@ -4,8 +4,6 @@
 # Licensed under the MIT license, see LICENSE.md for details.
 # SPDX-License-Identifier: MIT
 
-import warnings
-
 from lenskit.data import ItemList
 
 from .._base import ListMetric, Metric
@@ -18,12 +16,14 @@ class RankingMetricBase(Metric):
     Base class for most ranking metrics, implementing an ``n`` parameter for
     truncation.
 
+    .. versionchanged:: 2026.1
+
+        Removed deprecated ``k`` alias for ``n``.
+
     Args:
         n:
             Specify the length cutoff for rankings. Rankings longer than this
             will be truncated prior to measurement.
-        k:
-            Deprecated alias for ``n``.
 
     Stability:
         Caller
@@ -32,12 +32,7 @@ class RankingMetricBase(Metric):
     n: int | None = None
     "The maximum length of rankings to consider."
 
-    def __init__(self, n: int | None = None, *, k: int | None = None):
-        if n is None:
-            if k is not None:
-                warnings.warn("k= is deprecated, use n=", DeprecationWarning)
-                n = k
-
+    def __init__(self, n: int | None = None):
         if n is not None and n < 0:
             raise ValueError("n must be positive or None")
         self.n = n

src/lenskit/metrics/ranking/_dcg.py

@@ -78,12 +78,11 @@ def __init__(
         self,
         n: int | None = None,
         *,
-        k: int | None = None,
         weight: RankWeight = LogRankWeight(),
         discount: Discount | None = None,
         gain: str | None = None,
     ):
-        super().__init__(n, k=k)
+        super().__init__(n)
         self.weight = weight
         self.discount = discount
         if discount is not None:
@@ -174,12 +173,11 @@ def __init__(
         self,
         n: int | None = None,
         *,
-        k: int | None = None,
         weight: RankWeight = LogRankWeight(),
         discount: Discount | None = None,
         gain: str | None = None,
     ):
-        super().__init__(n, k=k)
+        super().__init__(n)
         self.weight = weight
         self.discount = discount
         if discount is not None:

src/lenskit/metrics/ranking/_gini.py

@@ -37,10 +37,9 @@ def __init__(
         self,
         n: int | None = None,
         *,
-        k: int | None = None,
         items: Vocabulary | Dataset,
     ):
-        super().__init__(n, k=k)
+        super().__init__(n)
         if isinstance(items, Dataset):
             self.item_vocab = items.items
         else:
@@ -100,11 +99,10 @@ def __init__(
         self,
         n: int | None = None,
         *,
-        k: int | None = None,
         items: Vocabulary | Dataset,
         weight: RankWeight = GeometricRankWeight(),
     ):
-        super().__init__(n=n, k=k, items=items)
+        super().__init__(n=n, items=items)
         self.weight = weight
 
     @override

src/lenskit/metrics/ranking/_pop.py

@@ -51,10 +51,9 @@ def __init__(
         data: Dataset,
         *,
         n: int | None = None,
-        k: int | None = None,
         count: Literal["users", "interactions"] = "users",
     ):
-        super().__init__(n, k=k)
+        super().__init__(n)
         stats = data.item_stats()
         match count:
             case "users":

src/lenskit/metrics/ranking/_rbp.py

@@ -104,13 +104,12 @@ def __init__(
         self,
         n: int | None = None,
         *,
-        k: int | None = None,
         weight: RankWeight | None = None,
         patience: float = 0.85,
         normalize: bool = False,
         weight_field: str | None = None,
     ):
-        super().__init__(n, k=k)
+        super().__init__(n)
         self.patience = patience
         if weight is None and weight_field is None:
             weight = GeometricRankWeight(patience)