python: fix already mutable borrowed append (#3943)

pola-rs · Jul 8, 2022 · 0377c80 · 0377c80
1 parent 05aacf9
commit 0377c80
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Showing 2 changed files with 16 additions and 4 deletions.
diff --git a/py-polars/polars/internals/series.py b/py-polars/polars/internals/series.py
@@ -1301,10 +1301,16 @@ def append(self, other: Series, append_chunks: bool = True) -> None:
         ]
 
         """
-        if append_chunks:
-            self._s.append(other._s)
-        else:
-            self._s.extend(other._s)
+        try:
+            if append_chunks:
+                self._s.append(other._s)
+            else:
+                self._s.extend(other._s)
+        except RuntimeError as e:
+            if str(e) == "Already mutably borrowed":
+                return self.append(other.clone(), append_chunks)
+            else:
+                raise e
 
     def filter(self, predicate: Series | list) -> Series:
         """

diff --git a/py-polars/tests/test_series.py b/py-polars/tests/test_series.py
@@ -1631,3 +1631,9 @@ def test_reverse() -> None:
 
     s = pl.Series("values", ["a", "b", None, "y", "x"])
     assert s.reverse().to_list() == ["x", "y", None, "b", "a"]
+
+
+def test_mutable_borrowed_append_3915() -> None:
+    s = pl.Series("s", [1, 2, 3])
+    s.append(s)
+    assert s.to_list() == [1, 2, 3, 1, 2, 3]