Validation for groupby arguments (#4176)

pola-rs · Jul 29, 2022 · 29598cc · 29598cc
1 parent 992da40
commit 29598cc
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diff --git a/py-polars/polars/internals/frame.py b/py-polars/polars/internals/frame.py
@@ -3104,6 +3104,10 @@ def groupby(
         └─────┴─────┴─────┘
 
         """
+        if not isinstance(maintain_order, bool):
+            raise TypeError(
+                f"invalid input for groupby arg `maintain_order`: {maintain_order}."
+            )
         if isinstance(by, str):
             by = [by]
         return GroupBy(

diff --git a/py-polars/tests/test_df.py b/py-polars/tests/test_df.py
@@ -419,6 +419,10 @@ def test_groupby() -> None:
     # assert df.groupby("b").quantile(0.5).shape == (2, 3)
     assert df.groupby("b").agg_list().shape == (2, 3)
 
+    # Invalid input: `by` not specified as a sequence
+    with pytest.raises(TypeError):
+        df.groupby("a", "b")  # type: ignore[arg-type]
+
 
 @pytest.mark.parametrize(
     "stack,exp_shape,exp_columns",