BUG: change test location (pandas-dev#39189)

Author: nofarmish

pandas/core/computation/pytables.py

@@ -210,8 +210,12 @@ def stringify(value):
                 v = Timedelta(v, unit="s").value
             return TermValue(int(v), v, kind)
         elif meta == "category":
-            term_value = self._convert_category_value(self.metadata, v)
-            return term_value
+            metadata = extract_array(self.metadata, extract_numpy=True)
+            if v not in metadata:
+                result = -1
+            else:
+                result = metadata.searchsorted(v, side="left")
+            return TermValue(result, result, "integer")
         elif kind == "integer":
             v = int(float(v))
             return TermValue(v, v, kind)
@@ -240,15 +244,6 @@ def stringify(value):
         else:
             raise TypeError(f"Cannot compare {v} of type {type(v)} to {kind} column")
 
-    @staticmethod
-    def _convert_category_value(metadata: Series, value: Any) -> TermValue:
-        metadata = extract_array(metadata, extract_numpy=True)
-        if value not in metadata:
-            result = -1
-        else:
-            result = metadata.searchsorted(value, side="left")
-        return TermValue(result, result, "integer")
-
     def convert_values(self):
         pass
 

pandas/tests/computation/test_pytables.py

@@ -184,3 +184,19 @@ def test_categorical_nan_only_columns(setup_path):
         df.to_hdf(path, "df", format="table", data_columns=True)
         result = read_hdf(path, "df")
         tm.assert_frame_equal(result, expected)
+
+
+@pytest.mark.parametrize(
+    "value, expected_results",
+    [
+        ('col=="q"', DataFrame({"col": ["a", "b", "s"]}, DataFrame({"col": []}))),
+        ('col=="a"', DataFrame({"col": ["a", "b", "s"]}, DataFrame({"col": ["a"]}))),
+    ],
+)
+def test_convert_value(setup_path, where: str, df: DataFrame, expected: DataFrame):
+    # GH39420
+    # Check that read_hdf with categorical columns can filter by where condition.
+    with ensure_clean_path(setup_path) as path:
+        df.to_hdf(path, "df", format="table")
+        result = read_hdf(path, "df", where=where)
+        tm.assert_frame_equal(result, expected)