fix(python): Fix decimal series dispatch (#20400)

py-polars/polars/series/series.py

@@ -1035,13 +1035,15 @@ def __add__(self, other: Expr) -> Expr: ...
     @overload
     def __add__(self, other: Any) -> Self: ...
 
-    def __add__(self, other: Any) -> Self | DataFrame | Expr:
+    def __add__(self, other: Any) -> Series | DataFrame | Expr:
         if isinstance(other, str):
             other = Series("", [other])
         elif isinstance(other, pl.DataFrame):
             return other + self
         elif isinstance(other, pl.Expr):
             return F.lit(self) + other
+        if self.dtype.is_decimal() and isinstance(other, (float, int)):
+            return self.to_frame().select(F.col(self.name) + other).to_series()
         return self._arithmetic(other, "add", "add_<>")
 
     @overload
@@ -1050,9 +1052,11 @@ def __sub__(self, other: Expr) -> Expr: ...
     @overload
     def __sub__(self, other: Any) -> Self: ...
 
-    def __sub__(self, other: Any) -> Self | Expr:
+    def __sub__(self, other: Any) -> Series | Expr:
         if isinstance(other, pl.Expr):
             return F.lit(self) - other
+        if self.dtype.is_decimal() and isinstance(other, (float, int)):
+            return self.to_frame().select(F.col(self.name) - other).to_series()
         return self._arithmetic(other, "sub", "sub_<>")
 
     def _recursive_cast_to_dtype(self, leaf_dtype: PolarsDataType) -> Series:
@@ -1083,6 +1087,8 @@ def __truediv__(self, other: Any) -> Series | Expr:
         if self.dtype.is_temporal():
             msg = "first cast to integer before dividing datelike dtypes"
             raise TypeError(msg)
+        if self.dtype.is_decimal() and isinstance(other, (float, int)):
+            return self.to_frame().select(F.col(self.name) / other).to_series()
 
         self = (
             self
@@ -1111,6 +1117,8 @@ def __floordiv__(self, other: Any) -> Series | Expr:
         if self.dtype.is_temporal():
             msg = "first cast to integer before dividing datelike dtypes"
             raise TypeError(msg)
+        if self.dtype.is_decimal() and isinstance(other, (float, int)):
+            return self.to_frame().select(F.col(self.name) // other).to_series()
 
         if not isinstance(other, pl.Expr):
             other = F.lit(other)
@@ -1134,6 +1142,8 @@ def __mul__(self, other: Any) -> Series | DataFrame | Expr:
         if self.dtype.is_temporal():
             msg = "first cast to integer before multiplying datelike dtypes"
             raise TypeError(msg)
+        if self.dtype.is_decimal() and isinstance(other, (float, int)):
+            return self.to_frame().select(F.col(self.name) * other).to_series()
         elif isinstance(other, pl.DataFrame):
             return other * self
         else:
@@ -1151,6 +1161,8 @@ def __mod__(self, other: Any) -> Series | Expr:
         if self.dtype.is_temporal():
             msg = "first cast to integer before applying modulo on datelike dtypes"
             raise TypeError(msg)
+        if self.dtype.is_decimal() and isinstance(other, (float, int)):
+            return self.to_frame().select(F.col(self.name) % other).to_series()
         return self._arithmetic(other, "rem", "rem_<>")
 
     def __rmod__(self, other: Any) -> Series:
@@ -1160,11 +1172,15 @@ def __rmod__(self, other: Any) -> Series:
         return self._arithmetic(other, "rem", "rem_<>_rhs")
 
     def __radd__(self, other: Any) -> Series:
-        if isinstance(other, str):
-            return (other + self.to_frame()).to_series()
+        if isinstance(other, str) or (
+            isinstance(other, (int, float)) and self.dtype.is_decimal()
+        ):
+            return self.to_frame().select(other + F.col(self.name)).to_series()
         return self._arithmetic(other, "add", "add_<>_rhs")
 
     def __rsub__(self, other: Any) -> Series:
+        if isinstance(other, (int, float)) and self.dtype.is_decimal():
+            return self.to_frame().select(other - F.col(self.name)).to_series()
         return self._arithmetic(other, "sub", "sub_<>_rhs")
 
     def __rtruediv__(self, other: Any) -> Series:
@@ -1173,6 +1189,8 @@ def __rtruediv__(self, other: Any) -> Series:
             raise TypeError(msg)
         if self.dtype.is_float():
             self.__rfloordiv__(other)
+        if isinstance(other, (int, float)) and self.dtype.is_decimal():
+            return self.to_frame().select(other / F.col(self.name)).to_series()
 
         if isinstance(other, int):
             other = float(other)
@@ -1188,6 +1206,8 @@ def __rmul__(self, other: Any) -> Series:
         if self.dtype.is_temporal():
             msg = "first cast to integer before multiplying datelike dtypes"
             raise TypeError(msg)
+        if isinstance(other, (int, float)) and self.dtype.is_decimal():
+            return self.to_frame().select(other * F.col(self.name)).to_series()
         return self._arithmetic(other, "mul", "mul_<>")
 
     def __pow__(self, exponent: int | float | Series) -> Series:

py-polars/tests/unit/dataframe/test_df.py

@@ -2038,6 +2038,7 @@ def test_add_string() -> None:
     expected = pl.DataFrame(
         {"a": ["hello hi", "hello there"], "b": ["hello hello", "hello world"]}
     )
+    print(expected)
     assert_frame_equal(("hello " + df), expected)
 
 

py-polars/tests/unit/datatypes/test_decimal.py

@@ -553,3 +553,26 @@ def test_decimal_arithmetic_schema() -> None:
     assert q1.collect_schema() == q1.collect().schema
     q1 = q.select(pl.col.x + pl.col.x)
     assert q1.collect_schema() == q1.collect().schema
+
+
+def test_decimal_arithmetic_schema_float_20369() -> None:
+    s = pl.Series("x", [1.0], dtype=pl.Decimal(15, 2))
+    assert_series_equal((s - 1.0), pl.Series("x", [0.0], dtype=pl.Decimal(None, 2)))
+    assert_series_equal(
+        (3.0 - s), pl.Series("literal", [2.0], dtype=pl.Decimal(None, 2))
+    )
+    assert_series_equal(
+        (3.0 / s), pl.Series("literal", [3.0], dtype=pl.Decimal(None, 6))
+    )
+    assert_series_equal(
+        (s / 3.0), pl.Series("x", [0.333333], dtype=pl.Decimal(None, 6))
+    )
+
+    assert_series_equal((s + 1.0), pl.Series("x", [2.0], dtype=pl.Decimal(None, 2)))
+    assert_series_equal(
+        (1.0 + s), pl.Series("literal", [2.0], dtype=pl.Decimal(None, 2))
+    )
+    assert_series_equal((s * 1.0), pl.Series("x", [1.0], dtype=pl.Decimal(None, 4)))
+    assert_series_equal(
+        (1.0 * s), pl.Series("literal", [1.0], dtype=pl.Decimal(None, 4))
+    )

py-polars/tests/unit/series/test_series.py

@@ -371,10 +371,11 @@ def test_categorical_agg(s: pl.Series, min: str | None, max: str | None) -> None
 def test_add_string() -> None:
     s = pl.Series(["hello", "weird"])
     result = s + " world"
+    print(result)
     assert_series_equal(result, pl.Series(["hello world", "weird world"]))
 
     result = "pfx:" + s
-    assert_series_equal(result, pl.Series(["pfx:hello", "pfx:weird"]))
+    assert_series_equal(result, pl.Series("literal", ["pfx:hello", "pfx:weird"]))
 
 
 @pytest.mark.parametrize(