columns property added in (#670)

Co-authored-by: Marco Edward Gorelli <marcogorelli@protonmail.com>

Author: benrutter

narwhals/_dask/dataframe.py

@@ -55,6 +55,10 @@ def collect(self) -> Any:
             backend_version=parse_version(get_pandas().__version__),
         )
 
+    @property
+    def columns(self) -> list[str]:
+        return self._native_dataframe.columns.tolist()  # type: ignore[no-any-return]
+
     def lazy(self) -> Self:
         return self
 

tests/dask_test.py

@@ -271,6 +271,16 @@ def test_str_to_lowercase(
     compare_dicts(result_frame, expected)
 
 
+def test_columns() -> None:
+    import dask.dataframe as dd
+
+    dfdd = dd.from_pandas(pd.DataFrame({"a": [1, 2, 3], "b": ["cat", "bat", "mat"]}))
+    df = nw.from_native(dfdd)
+
+    result = df.columns
+    assert result == ["a", "b"]
+
+
 def test_select() -> None:
     import dask.dataframe as dd