ARROW-9917: [Python][Compute] Bindings for mode kernel

python/pyarrow/compute.py

@@ -183,6 +183,32 @@ def sum(array):
     return call_function('sum', [array])
 
 
+def mode(array):
+    """
+    Return the mode (most common value) of a passed numerical
+    (chunked) array. If there is more than one such value, only
+    the smallest is returned.
+
+    Parameters
+    ----------
+    array : pyarrow.Array or pyarrow.ChunkedArray
+
+    Returns
+    -------
+    mode : pyarrow.StructScalar
+
+    Examples
+    --------
+    >>> import pyarrow as pa
+    >>> import pyarrow.compute as pc
+    >>> arr = pa.array([1, 1, 2, 2, 3, 2, 2, 2])
+    >>> pc.mode(arr)
+    <pyarrow.StructScalar: {'mode': 2, 'count': 5}>
+
+    """
+    return call_function("mode", [array])
+
+
 def filter(data, mask, null_selection_behavior='drop'):
     """
     Select values (or records) from array- or table-like data given boolean

python/pyarrow/tests/test_compute.py

@@ -109,6 +109,31 @@ def test_sum_chunked_array(arrow_type):
     assert pc.sum(arr).as_py() is None  # noqa: E711
 
 
+def test_mode_array():
+    # ARROW-9917
+
+    arr = pa.array([1, 1, 3, 4, 3, 5], type='int64')
+    expected = {"mode": 1, "count": 2}
+    assert pc.mode(arr).as_py() == {"mode": 1, "count": 2}
+
+    arr = pa.array([], type='int64')
+    expected = {"mode": None, "count": None}
+    assert pc.mode(arr).as_py() == expected
+
+
+def test_mode_chunked_array():
+    # ARROW-9917
+
+    arr = pa.chunked_array([pa.array([1, 1, 3, 4, 3, 5], type='int64')])
+    expected = {"mode": 1, "count": 2}
+    assert pc.mode(arr).as_py() == expected
+
+    arr = pa.chunked_array((), type='int64')
+    expected = {"mode": None, "count": None}
+    assert arr.num_chunks == 0
+    assert pc.mode(arr).as_py() == expected
+
+
 def test_match_substring():
     arr = pa.array(["ab", "abc", "ba", None])
     result = pc.match_substring(arr, "ab")