python: __rpow__ and value error on datelike arithmetic

py-polars/polars/internals/series.py

@@ -55,6 +55,7 @@
 from polars.datatypes import List as PlList
 from polars.datatypes import (
     Object,
+    Time,
     UInt8,
     UInt16,
     UInt32,
@@ -356,25 +357,40 @@ def __sub__(self, other: Any) -> "Series":
         return self._arithmetic(other, "sub", "sub_<>")
 
     def __truediv__(self, other: Any) -> "Series":
+        if self.is_datelike():
+            raise ValueError("first cast to integer before dividing datelike dtypes")
+
         # this branch is exactly the floordiv function without rounding the floats
         if self.is_float():
             return self._arithmetic(other, "div", "div_<>")
 
         return self.cast(Float64) / other
 
     def __floordiv__(self, other: Any) -> "Series":
+        if self.is_datelike():
+            raise ValueError("first cast to integer before dividing datelike dtypes")
         result = self._arithmetic(other, "div", "div_<>")
         if self.is_float():
             result = result.floor()
         return result
 
     def __mul__(self, other: Any) -> "Series":
+        if self.is_datelike():
+            raise ValueError("first cast to integer before multiplying datelike dtypes")
         return self._arithmetic(other, "mul", "mul_<>")
 
     def __mod__(self, other: Any) -> "Series":
+        if self.is_datelike():
+            raise ValueError(
+                "first cast to integer before applying modulo on datelike dtypes"
+            )
         return self._arithmetic(other, "rem", "rem_<>")
 
     def __rmod__(self, other: Any) -> "Series":
+        if self.is_datelike():
+            raise ValueError(
+                "first cast to integer before applying modulo on datelike dtypes"
+            )
         return self._arithmetic(other, "rem", "rem_<>_rhs")
 
     def __radd__(self, other: Any) -> "Series":
@@ -389,6 +405,8 @@ def __invert__(self) -> "Series":
         return NotImplemented
 
     def __rtruediv__(self, other: Any) -> np.ndarray:
+        if self.is_datelike():
+            raise ValueError("first cast to integer before dividing datelike dtypes")
         if self.is_float():
             self.__rfloordiv__(other)
 
@@ -398,14 +416,29 @@ def __rtruediv__(self, other: Any) -> np.ndarray:
         return self.cast(Float64).__rfloordiv__(other)  # type: ignore
 
     def __rfloordiv__(self, other: Any) -> "Series":
+        if self.is_datelike():
+            raise ValueError("first cast to integer before dividing datelike dtypes")
         return self._arithmetic(other, "div", "div_<>_rhs")
 
     def __rmul__(self, other: Any) -> "Series":
+        if self.is_datelike():
+            raise ValueError("first cast to integer before multiplying datelike dtypes")
         return self._arithmetic(other, "mul", "mul_<>")
 
     def __pow__(self, power: float, modulo: None = None) -> "Series":
+        if self.is_datelike():
+            raise ValueError(
+                "first cast to integer before raising datelike dtypes to a power"
+            )
         return np.power(self, power)  # type: ignore
 
+    def __rpow__(self, other: Any) -> "Series":
+        if self.is_datelike():
+            raise ValueError(
+                "first cast to integer before raising datelike dtypes to a power"
+            )
+        return np.power(other, self)  # type: ignore
+
     def __neg__(self) -> "Series":
         return 0 - self
 
@@ -1847,7 +1880,7 @@ def is_datelike(self) -> bool:
         True
 
         """
-        return self.dtype in (Date, Datetime, Duration)
+        return self.dtype in (Date, Datetime, Duration, Time)
 
     def is_float(self) -> bool:
         """

py-polars/tests/test_series.py

@@ -182,6 +182,28 @@ def test_arithmetic(s: pl.Series) -> None:
     assert ((1.0 + a) == [2, 3]).sum() == 2
     assert ((1.0 % a) == [0, 1]).sum() == 2
 
+    a = pl.Series("a", [datetime(2021, 1, 1)])
+    with pytest.raises(ValueError):
+        a // 2
+    with pytest.raises(ValueError):
+        a / 2
+    with pytest.raises(ValueError):
+        a * 2
+    with pytest.raises(ValueError):
+        a % 2
+    with pytest.raises(ValueError):
+        a ** 2
+    with pytest.raises(ValueError):
+        2 / a
+    with pytest.raises(ValueError):
+        2 // a
+    with pytest.raises(ValueError):
+        2 * a
+    with pytest.raises(ValueError):
+        2 % a
+    with pytest.raises(ValueError):
+        2 ** a
+
 
 def test_add_string() -> None:
     s = pl.Series(["hello", "weird"])