Enhance DataFrame.sort method to accept column names as sorting expressions

Author: kosiew

python/datafusion/dataframe.py

@@ -521,19 +521,22 @@ def aggregate(
         aggs = [e.expr for e in aggs]
         return DataFrame(self.df.aggregate(group_by, aggs))
 
-    def sort(self, *exprs: Expr | SortExpr) -> DataFrame:
-        """Sort the DataFrame by the specified sorting expressions.
+    def sort(self, *exprs: Expr | SortExpr | str) -> DataFrame:
+        """Sort the DataFrame by the specified sorting expressions or column names.
 
         Note that any expression can be turned into a sort expression by
-        calling its` ``sort`` method.
+        calling its ``sort`` method.
 
         Args:
-            exprs: Sort expressions, applied in order.
+            exprs: Sort expressions or column names, applied in order.
 
         Returns:
             DataFrame after sorting.
         """
-        exprs_raw = [sort_or_default(expr) for expr in exprs]
+        exprs_raw = []
+        for expr in exprs:
+            expr_obj = Expr.column(expr).sort() if isinstance(expr, str) else expr
+            exprs_raw.append(sort_or_default(expr_obj))
         return DataFrame(self.df.sort(*exprs_raw))
 
     def cast(self, mapping: dict[str, pa.DataType[Any]]) -> DataFrame: