Add strict parameter to lit

py-polars/polars/functions/lit.py

@@ -25,7 +25,11 @@
 
 
 def lit(
-    value: Any, dtype: PolarsDataType | None = None, *, allow_object: bool = False
+    value: Any,
+    dtype: PolarsDataType | None = None,
+    *,
+    allow_object: bool = False,
+    strict: bool = True,
 ) -> Expr:
     """
     Return an expression representing a literal value.
@@ -41,6 +45,10 @@ def lit(
         If type is unknown use an 'object' type.
         By default, we will raise a `ValueException`
         if the type is unknown.
+    strict : bool, default True
+        Throw an error if any value does not exactly match the given or inferred data
+        type. If set to `False`, values that do not match the data type are cast to
+        that data type or, if casting is not possible, set to null instead.
 
     Notes
     -----
@@ -147,7 +155,7 @@ def lit(
         return lit(pl.Series("literal", value, dtype=dtype))
 
     elif isinstance(value, (list, tuple)):
-        return lit(pl.Series("literal", [value], dtype=dtype))
+        return lit(pl.Series("literal", [value], dtype=dtype, strict=strict))
 
     elif isinstance(value, enum.Enum):
         lit_value = value.value

py-polars/tests/unit/expr/test_exprs.py

@@ -417,6 +417,17 @@ def lit_series(value: Any, dtype: PolarsDataType | None) -> pl.Series:
     )
 
 
+def test_lit_strict() -> None:
+    # Default is strict = False
+    with pytest.raises(TypeError, match="unexpected value while building Series"):
+        pl.select(pl.lit([1, 1.0]))
+
+    assert_series_equal(
+        pl.select(pl.lit([1, 1.0], strict=False).alias("a")).to_series(),
+        pl.Series("a", [[1.0, 1.0]]),
+    )
+
+
 def test_lit_empty_tu() -> None:
     td = timedelta(1)
     assert pl.select(pl.lit(td, dtype=pl.Duration)).item() == td