python DataFrame.with_column -> pl.Series

py-polars/docs/source/reference/dataframe.rst

@@ -91,6 +91,7 @@ Manipulation/ selection
     DataFrame.select_at_idx
     DataFrame.clone
     DataFrame.get_columns
+    DataFrame.get_column
     DataFrame.fill_null
     DataFrame.fill_nan
     DataFrame.explode

py-polars/polars/eager/frame.py

@@ -2209,6 +2209,12 @@ def get_columns(self) -> tp.List["pl.Series"]:
         """
         return list(map(lambda s: pl.eager.series.wrap_s(s), self._df.get_columns()))
 
+    def get_column(self, name: str) -> "pl.Series":
+        """
+        Get a single column as Series by name.
+        """
+        return self[name]
+
     def fill_null(self, strategy: Union[str, "pl.Expr"]) -> "DataFrame":
         """
         Fill None/missing values by a filling strategy or an Expression evaluation.

py-polars/tests/test_df.py

@@ -209,10 +209,13 @@ def test_init_records():
 def test_selection():
     df = pl.DataFrame({"a": [1, 2, 3], "b": [1.0, 2.0, 3.0], "c": ["a", "b", "c"]})
 
+    # get_column by name
+    assert df.get_column("a").to_list() == [1, 2, 3]
+
     # column selection by string(s) in first dimension
-    assert df["a"] == [1, 2, 3]
-    assert df["b"] == [1.0, 2.0, 3.0]
-    assert df["c"] == ["a", "b", "c"]
+    assert df["a"].to_list() == [1, 2, 3]
+    assert df["b"].to_list() == [1.0, 2.0, 3.0]
+    assert df["c"].to_list() == ["a", "b", "c"]
 
     # row selection by integers(s) in first dimension
     assert df[0].frame_equal(pl.DataFrame({"a": [1], "b": [1.0], "c": ["a"]}))