add warning to always-null comparisons

pola-rs · ritchie46 · Nov 30, 2023 · Oct 16, 2023 · Oct 16, 2023 · Oct 17, 2023
commit 33f09b968cca77eac5361821c62f866d5ee180d5
@@ -93,6 +93,7 @@
 from polars.utils.various import (
     _prepare_row_count_args,
     _process_null_values,
+    _warn_null_comparison,
     can_create_dicts_with_pyarrow,
     handle_projection_columns,
     is_bool_sequence,
@@ -1450,21 +1451,27 @@ def __bool__(self) -> NoReturn:
         )
 
     def __eq__(self, other: Any) -> DataFrame:  # type: ignore[override]
+        _warn_null_comparison(other)
         return self._comp(other, "eq")
 
     def __ne__(self, other: Any) -> DataFrame:  # type: ignore[override]
+        _warn_null_comparison(other)
         return self._comp(other, "neq")
 
     def __gt__(self, other: Any) -> DataFrame:
+        _warn_null_comparison(other)
         return self._comp(other, "gt")
 
     def __lt__(self, other: Any) -> DataFrame:
+        _warn_null_comparison(other)
         return self._comp(other, "lt")
 
     def __ge__(self, other: Any) -> DataFrame:
+        _warn_null_comparison(other)
         return self._comp(other, "gt_eq")
 
     def __le__(self, other: Any) -> DataFrame:
+        _warn_null_comparison(other)
         return self._comp(other, "lt_eq")
 
     def __getstate__(self) -> list[Series]:

@@ -58,7 +58,7 @@
     warn_closed_future_change,
 )
 from polars.utils.meta import threadpool_size
-from polars.utils.various import no_default, sphinx_accessor
+from polars.utils.various import no_default, sphinx_accessor, _warn_null_comparison
 
 with contextlib.suppress(ImportError):  # Module not available when building docs
     from polars.polars import arg_where as py_arg_where
@@ -159,6 +159,7 @@ def __rand__(self, other: Any) -> Self:
         return self._from_pyexpr(self._to_pyexpr(other)._and(self._pyexpr))
 
     def __eq__(self, other: Any) -> Self:  # type: ignore[override]
+        _warn_null_comparison(other)
         return self._from_pyexpr(self._pyexpr.eq(self._to_pyexpr(other)))
 
     def __floordiv__(self, other: Any) -> Self:
@@ -168,18 +169,22 @@ def __rfloordiv__(self, other: Any) -> Self:
         return self._from_pyexpr(self._to_pyexpr(other) // self._pyexpr)
 
     def __ge__(self, other: Any) -> Self:
+        _warn_null_comparison(other)
         return self._from_pyexpr(self._pyexpr.gt_eq(self._to_pyexpr(other)))
 
     def __gt__(self, other: Any) -> Self:
+        _warn_null_comparison(other)
         return self._from_pyexpr(self._pyexpr.gt(self._to_pyexpr(other)))
 
     def __invert__(self) -> Self:
         return self.not_()
 
     def __le__(self, other: Any) -> Self:
+        _warn_null_comparison(other)
         return self._from_pyexpr(self._pyexpr.lt_eq(self._to_pyexpr(other)))
 
     def __lt__(self, other: Any) -> Self:
+        _warn_null_comparison(other)
         return self._from_pyexpr(self._pyexpr.lt(self._to_pyexpr(other)))
 
     def __mod__(self, other: Any) -> Self:
@@ -195,6 +200,7 @@ def __rmul__(self, other: Any) -> Self:
         return self._from_pyexpr(self._to_pyexpr(other) * self._pyexpr)
 
     def __ne__(self, other: Any) -> Self:  # type: ignore[override]
+        _warn_null_comparison(other)
         return self._from_pyexpr(self._pyexpr.neq(self._to_pyexpr(other)))
 
     def __neg__(self) -> Expr:

@@ -101,6 +101,7 @@
     range_to_slice,
     scale_bytes,
     sphinx_accessor,
+    _warn_null_comparison
 )
 
 with contextlib.suppress(ImportError):  # Module not available when building docs
@@ -559,6 +560,7 @@ def __eq__(self, other: Any) -> Series:
         ...
 
     def __eq__(self, other: Any) -> Series | Expr:
+        _warn_null_comparison(other)
         if isinstance(other, pl.Expr):
             return F.lit(self).__eq__(other)
         return self._comp(other, "eq")
@@ -572,6 +574,7 @@ def __ne__(self, other: Any) -> Series:
         ...
 
     def __ne__(self, other: Any) -> Series | Expr:
+        _warn_null_comparison(other)
         if isinstance(other, pl.Expr):
             return F.lit(self).__ne__(other)
         return self._comp(other, "neq")
@@ -585,6 +588,7 @@ def __gt__(self, other: Any) -> Series:
         ...
 
     def __gt__(self, other: Any) -> Series | Expr:
+        _warn_null_comparison(other)
         if isinstance(other, pl.Expr):
             return F.lit(self).__gt__(other)
         return self._comp(other, "gt")
@@ -598,6 +602,7 @@ def __lt__(self, other: Any) -> Series:
         ...
 
     def __lt__(self, other: Any) -> Series | Expr:
+        _warn_null_comparison(other)
         if isinstance(other, pl.Expr):
             return F.lit(self).__lt__(other)
         return self._comp(other, "lt")
@@ -611,6 +616,7 @@ def __ge__(self, other: Any) -> Series:
         ...
 
     def __ge__(self, other: Any) -> Series | Expr:
+        _warn_null_comparison(other)
         if isinstance(other, pl.Expr):
             return F.lit(self).__ge__(other)
         return self._comp(other, "gt_eq")
@@ -624,6 +630,7 @@ def __le__(self, other: Any) -> Series:
         ...
 
     def __le__(self, other: Any) -> Series | Expr:
+        _warn_null_comparison(other)
         if isinstance(other, pl.Expr):
             return F.lit(self).__le__(other)
         return self._comp(other, "lt_eq")

@@ -121,6 +121,15 @@ def is_str_sequence(
     return isinstance(val, Sequence) and _is_iterable_of(val, str)
 
 
+def _warn_null_comparison(obj: Any):
+    if obj is None:
+        warnings.warn(
+            f"comparisons with None always result in null, consider using .is_null() or .is_not_null()",
+            UserWarning,
+            stacklevel=find_stacklevel(),
+        )
+
+
 def range_to_series(
     name: str, rng: range, dtype: PolarsIntegerType | None = None
 ) -> pl.Series: