From 7b1299b957e4f03d439f5f4f338c22458df6d9a1 Mon Sep 17 00:00:00 2001
From: MarcoGorelli <33491632+MarcoGorelli@users.noreply.github.com>
Date: Wed, 6 Dec 2023 18:12:01 +0000
Subject: [PATCH] add column.n_unique

---
 spec/API_specification/dataframe_api/column_object.py | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/spec/API_specification/dataframe_api/column_object.py b/spec/API_specification/dataframe_api/column_object.py
index b3e10738..1270427b 100644
--- a/spec/API_specification/dataframe_api/column_object.py
+++ b/spec/API_specification/dataframe_api/column_object.py
@@ -750,6 +750,17 @@ def var(
         """
         ...
 
+    def n_unique(self, *, skip_nulls: bool = True) -> Scalar:
+        """Return number of unique values.
+
+        Notes
+        -----
+        If the original column(s) contain multiple `'NaN'` values, then
+        they only count as one distinct value.
+        Likewise for null values (if ``skip_nulls=False``).
+        """
+        ...
+
     def cumulative_max(self) -> Self:
         """Reduction returns a Column.