amol- commented on a change in pull request #11624:
URL: https://github.com/apache/arrow/pull/11624#discussion_r746782346
##########
File path: python/pyarrow/tests/test_table.py
##########
@@ -1746,3 +1746,48 @@ def test_table_select():
result = table.select(['f2'])
expected = pa.table([a2], ['f2'])
assert result.equals(expected)
+
+
+def test_table_group_by():
+ table = pa.table([
+ pa.array([1, 2, 3, 4, 5]),
+ pa.array(["a", "a", "b", "b", "c"]),
+ ], names=["values", "keys"])
+
+ r = table.group_by("keys", ["values"], "hash_sum")
+ assert r.to_pydict() == {
+ "key_0": ["a", "b", "c"],
+ "sum": [3, 7, 5]
+ }
+
+ r = table.group_by("keys", ["values", "values"], [
+ "hash_sum", "hash_count"])
+ assert r.to_pydict() == {
+ "key_0": ["a", "b", "c"],
+ "sum": [3, 7, 5],
+ "count": [2, 2, 1]
+ }
Review comment:
You would get columns with duplicate names (two `sum` columns). At that
point it would be hard to tell what they refer to. I did an improvement in
https://github.com/apache/arrow/pull/11624/commits/30b64fe45bc3318ab59ad39194b5a5a12226aba9
where column names are named after the column they refer to, so if you are
asking two sums for two different columns you would get `col1_sum` and
`col2_sum` making obvious what they refer to.
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