GH-53500: [Python][Parquet] Prevent crashes when comparing metadata with None

python/pyarrow/_parquet.pyx

@@ -108,7 +108,7 @@ cdef class Statistics(_Weakrefable):
         except TypeError:
             return NotImplemented
 
-    def equals(self, Statistics other):
+    def equals(self, Statistics other not None):
         """
         Return whether the two column statistics objects are equal.
 
@@ -521,7 +521,7 @@ cdef class ColumnChunkMetaData(_Weakrefable):
         except TypeError:
             return NotImplemented
 
-    def equals(self, ColumnChunkMetaData other):
+    def equals(self, ColumnChunkMetaData other not None):
         """
         Return whether the two column chunk metadata objects are equal.
 
@@ -919,7 +919,7 @@ cdef class RowGroupMetaData(_Weakrefable):
         except TypeError:
             return NotImplemented
 
-    def equals(self, RowGroupMetaData other):
+    def equals(self, RowGroupMetaData other not None):
         """
         Return whether the two row group metadata objects are equal.
 
@@ -1295,7 +1295,7 @@ cdef class ParquetSchema(_Weakrefable):
         except TypeError:
             return NotImplemented
 
-    def equals(self, ParquetSchema other):
+    def equals(self, ParquetSchema other not None):
         """
         Return whether the two schemas are equal.
 
@@ -1350,7 +1350,7 @@ cdef class ColumnSchema(_Weakrefable):
     def __reduce__(self):
         return ColumnSchema, (self.parent, self.index)
 
-    def equals(self, ColumnSchema other):
+    def equals(self, ColumnSchema other not None):
         """
         Return whether the two column schemas are equal.
 

python/pyarrow/tests/parquet/test_metadata.py

@@ -724,6 +724,30 @@ def test_metadata_equals():
         original_metadata.equals(None)
 
 
+def test_parquet_metadata_equals_none(tempdir):
+    table = pa.table({"a": [1, 2, 3]})
+    path = tempdir / "metadata_equals_none.parquet"
+    pq.write_table(table, path)
+
+    metadata = pq.read_metadata(path)
+    row_group = metadata.row_group(0)
+    column_chunk = row_group.column(0)
+    objects = [
+        column_chunk.statistics,
+        column_chunk,
+        row_group,
+        metadata.schema,
+        metadata.schema[0],
+    ]
+    none_value = None
+
+    for obj in objects:
+        assert (obj == none_value) is False
+        assert (obj != none_value) is True
+        with pytest.raises(TypeError):
+            obj.equals(none_value)
+
+
 @pytest.mark.parametrize("t1,t2,expected_error", (
     ({'col1': range(10)}, {'col1': range(10)}, None),
     ({'col1': range(10)}, {'col2': range(10)},