feat: add utf8_literal function to create UTF8 literal expressions

Author: kosiew

python/datafusion/__init__.py

@@ -107,6 +107,11 @@ def literal(value):
     return Expr.literal(value)
 
 
+def utf8_literal(value):
+    """Create a UTF8 literal expression."""
+    return Expr.utf8_literal(value)
+
+
 def lit(value):
     """Create a literal expression."""
     return Expr.literal(value)

python/datafusion/expr.py

@@ -380,6 +380,12 @@ def literal(value: Any) -> Expr:
             value = pa.scalar(value)
         return Expr(expr_internal.Expr.literal(value))
 
+    @staticmethod
+    def utf8_literal(value: str) -> Expr:
+        """Creates a new expression representing a UTF8 literal value."""
+        value = pa.scalar(value, type=pa.string())
+        return Expr(expr_internal.Expr.literal(value))
+
     @staticmethod
     def column(value: str) -> Expr:
         """Creates a new expression representing a column."""

python/tests/test_functions.py

@@ -23,7 +23,9 @@
 
 from datafusion import SessionContext, column
 from datafusion import functions as f
-from datafusion import literal
+from datafusion import literal, utf8_literal
+from datafusion import Expr
+from datafusion.expr import expr_internal
 
 np.seterr(invalid="ignore")
 
@@ -907,8 +909,8 @@ def test_temporal_functions(df):
 
 def test_arrow_cast(df):
     df = df.select(
-        f.arrow_cast(column("a"), literal("Float64")).alias("a_as_float"),
-        f.arrow_cast(column("a"), literal("Int32")).alias("a_as_int"),
+        f.arrow_cast(column("a"), utf8_literal("Float64")).alias("a_as_float"),
+        f.arrow_cast(column("a"), utf8_literal("Int32")).alias("a_as_int"),
     )
     result = df.collect()
     assert len(result) == 1