first value_counts commit

Author: tpackard1

pandas/core/frame.py

@@ -6932,7 +6932,7 @@ def value_counts(
 
         Parameters
         ----------
-        subset : list-like, optional
+        subset : mapping, function, label, list of labels, optional
             Columns to use when counting unique combinations.
         normalize : bool, default False
             Return proportions rather than frequencies.
@@ -7024,6 +7024,13 @@ def value_counts(
         John        Smith          1
                     NaN            1
         dtype: int64
+
+        >>> df.value_counts("first_name")
+        first_name
+        John    2
+        Anne    1
+        Beth    1
+        dtype: int64
         """
         if subset is None:
             subset = self.columns.tolist()

pandas/tests/frame/methods/test_value_counts.py

@@ -144,3 +144,22 @@ def test_data_frame_value_counts_dropna_false(nulls_fixture):
     )
 
     tm.assert_series_equal(result, expected)
+
+
+def test_data_frame_value_counts_subset(nulls_fixture):
+    # GH 50829
+    df = pd.DataFrame(
+        {
+            "first_name": ["John", "Anne", "John", "Beth"],
+            "middle_name": ["Smith", nulls_fixture, nulls_fixture, "Louise"],
+        },
+    )
+    result = df.value_counts("first_name")
+    expected = pd.Series(
+        data=[2, 1, 1],
+        index=pd.MultiIndex.from_arrays(
+            [["John", "Anne", "Beth"]], names=["first_name"]
+        ),
+    )
+
+    tm.assert_series_equal(result, expected)