From 44298d9a1906c2e000a8873dad555295a5350c9d Mon Sep 17 00:00:00 2001
From: Bela Stoyan <bela.stoyan@gmail.com>
Date: Tue, 10 Sep 2024 10:26:27 +0200
Subject: [PATCH] use IO[bytes] instead of BytesIO

---
 py-polars/polars/dataframe/frame.py     |  2 +-
 py-polars/tests/unit/io/test_parquet.py | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/py-polars/polars/dataframe/frame.py b/py-polars/polars/dataframe/frame.py
index 2d8710b9f431..00fe52cba54a 100644
--- a/py-polars/polars/dataframe/frame.py
+++ b/py-polars/polars/dataframe/frame.py
@@ -3638,7 +3638,7 @@ def write_ipc_stream(
 
     def write_parquet(
         self,
-        file: str | Path | BytesIO,
+        file: str | Path | IO[bytes],
         *,
         compression: ParquetCompression = "zstd",
         compression_level: int | None = None,
diff --git a/py-polars/tests/unit/io/test_parquet.py b/py-polars/tests/unit/io/test_parquet.py
index 3da465561bd1..170cc2a015be 100644
--- a/py-polars/tests/unit/io/test_parquet.py
+++ b/py-polars/tests/unit/io/test_parquet.py
@@ -1891,3 +1891,16 @@ def test_concat_multiple_inmem() -> None:
 
     assert_frame_equal(pl.read_parquet([fb, gb]), dfs)
     assert_frame_equal(pl.read_parquet([fb, gb], use_pyarrow=True), dfs)
+
+
+@pytest.mark.write_disk
+def test_write_binary_open_file(tmp_path: Path) -> None:
+    df = pl.DataFrame({"a": [1, 2, 3]})
+
+    path = tmp_path / "test.parquet"
+
+    with path.open("wb") as f_write:
+        df.write_parquet(f_write)
+
+    out = pl.read_parquet(path)
+    assert_frame_equal(out, df)