Add Expr.reverse() Py API example (#3660)

pola-rs · Jun 11, 2022 · ef4d7fc · ef4d7fc
1 parent f5ba137
commit ef4d7fc
Showing 1 changed file with 32 additions and 0 deletions.
diff --git a/py-polars/polars/internals/expr.py b/py-polars/polars/internals/expr.py
@@ -1299,6 +1299,38 @@ def backward_fill(self, limit: Optional[int] = None) -> "Expr":
     def reverse(self) -> "Expr":
         """
         Reverse the selection.
+
+        >>> df = pl.DataFrame(
+        ...     {
+        ...         "A": [1, 2, 3, 4, 5],
+        ...         "fruits": ["banana", "banana", "apple", "apple", "banana"],
+        ...         "B": [5, 4, 3, 2, 1],
+        ...         "cars": ["beetle", "audi", "beetle", "beetle", "beetle"],
+        ...     }
+        ... )
+        >>> df.select(
+        ...     [
+        ...         pl.all(),
+        ...         pl.all().reverse().suffix("_reverse"),
+        ...     ]
+        ... )
+        shape: (5, 8)
+        ┌─────┬────────┬─────┬────────┬───────────┬────────────────┬───────────┬──────────────┐
+        │ A   ┆ fruits ┆ B   ┆ cars   ┆ A_reverse ┆ fruits_reverse ┆ B_reverse ┆ cars_reverse │
+        │ --- ┆ ---    ┆ --- ┆ ---    ┆ ---       ┆ ---            ┆ ---       ┆ ---          │
+        │ i64 ┆ str    ┆ i64 ┆ str    ┆ i64       ┆ str            ┆ i64       ┆ str          │
+        ╞═════╪════════╪═════╪════════╪═══════════╪════════════════╪═══════════╪══════════════╡
+        │ 1   ┆ banana ┆ 5   ┆ beetle ┆ 5         ┆ banana         ┆ 1         ┆ beetle       │
+        ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
+        │ 2   ┆ banana ┆ 4   ┆ audi   ┆ 4         ┆ apple          ┆ 2         ┆ beetle       │
+        ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
+        │ 3   ┆ apple  ┆ 3   ┆ beetle ┆ 3         ┆ apple          ┆ 3         ┆ beetle       │
+        ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
+        │ 4   ┆ apple  ┆ 2   ┆ beetle ┆ 2         ┆ banana         ┆ 4         ┆ audi         │
+        ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
+        │ 5   ┆ banana ┆ 1   ┆ beetle ┆ 1         ┆ banana         ┆ 5         ┆ beetle       │
+        └─────┴────────┴─────┴────────┴───────────┴────────────────┴───────────┴──────────────┘
+
         """
         return wrap_expr(self._pyexpr.reverse())