ignore index column in empty pandas dataframe (#2712)

py-polars/polars/internals/frame.py

@@ -359,7 +359,14 @@ def _from_pandas(
         """
         # path for table without rows that keeps datatype
         if data.shape[0] == 0:
-            return DataFrame([pli.Series(name, data[name]) for name in data.columns])
+            # We do a loop and materialize the series.
+            # There can be series of len != null due to pandas indexes.
+            series = []
+            for name in data.columns:
+                col = pli.Series(name, data[name])
+                if len(col) == 0:
+                    series.append(pli.Series(name, col))
+            return DataFrame(series)
 
         return cls._from_pydf(
             pandas_to_pydf(

py-polars/tests/test_interop.py

@@ -198,3 +198,10 @@ def test_from_empty_arrow() -> None:
     df = pl.from_arrow(pa.table(pd.DataFrame({"a": [], "b": []})))
     assert df.columns == ["a", "b"]  # type: ignore
     assert df.dtypes == [pl.Float64, pl.Float64]  # type: ignore
+
+    # 2705
+    df1 = pd.DataFrame(columns=["b"], dtype=float)
+    tbl = pa.Table.from_pandas(df1)
+    out = pl.from_arrow(tbl)
+    assert out.columns == ["b"]  # type: ignore
+    assert out.dtypes == [pl.Float64]  # type: ignore