Refactor _simplify_expression method to enhance type checking for expressions and improve error handling

Author: kosiew

python/datafusion/dataframe.py

@@ -476,21 +476,22 @@ def with_columns(
         def _simplify_expression(
             *exprs: Expr | Iterable[Expr], **named_exprs: Expr
         ) -> list[expr_internal.Expr]:
-            expr_list = []
+            expr_list: list[expr_internal.Expr] = []
             for expr in exprs:
-                if isinstance(expr, str):
+                if isinstance(expr, str) or (
+                    isinstance(expr, Iterable)
+                    and not isinstance(expr, Expr)
+                    and any(isinstance(inner, str) for inner in expr)
+                ):
                     raise TypeError(_EXPR_TYPE_ERROR)
-                if isinstance(expr, Iterable) and not isinstance(expr, Expr):
-                    if any(not isinstance(inner_expr, Expr) for inner_expr in expr):
-                        raise TypeError(_EXPR_TYPE_ERROR)
-                elif not isinstance(expr, Expr):
+                try:
+                    expr_list.extend(expr_list_to_raw_expr_list(expr))
+                except TypeError as err:
+                    raise TypeError(_EXPR_TYPE_ERROR) from err
+            for alias, expr in named_exprs.items():
+                if not isinstance(expr, Expr):
                     raise TypeError(_EXPR_TYPE_ERROR)
-                expr_list.extend(expr_list_to_raw_expr_list(expr))
-            if named_exprs:
-                for alias, expr in named_exprs.items():
-                    if not isinstance(expr, Expr):
-                        raise TypeError(_EXPR_TYPE_ERROR)
-                    expr_list.append(expr.alias(alias).expr)
+                expr_list.append(expr.alias(alias).expr)
             return expr_list
 
         expressions = _simplify_expression(*exprs, **named_exprs)