Add type check for filter predicates in DataFrame.filter method

Author: kosiew

python/datafusion/dataframe.py

@@ -426,6 +426,12 @@ def filter(self, *predicates: Expr) -> DataFrame:
         """
         df = self.df
         for p in predicates:
+            if not isinstance(p, Expr):
+                msg = (
+                    f"Expected Expr, got {type(p).__name__}. "
+                    "Use col() or lit() to construct expressions."
+                )
+                raise TypeError(msg)
             df = df.filter(p.expr)
         return DataFrame(df)
 

python/tests/test_dataframe.py

@@ -277,7 +277,7 @@ def test_sort_string_and_expression_equivalent(df):
 
 
 def test_filter_string_unsupported(df):
-    with pytest.raises(AttributeError):
+    with pytest.raises(TypeError, match=r"col\(\) or lit\(\)"):
         df.filter("a > 1")