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

@@ -19,6 +19,7 @@
 import decimal
 from collections import OrderedDict
 import io
+import operator
 
 try:
     import numpy as np
@@ -712,16 +713,36 @@ def test_metadata_schema_filesystem(tempdir):
             fname, filesystem=LocalFileSystem()).equals(schema)
 
 
-def test_metadata_equals():
+@pytest.mark.parametrize("kind", [
+    "file", "row_group", "column_chunk", "statistics", "schema", "column_schema"
+])
+def test_metadata_equals(kind):
     table = pa.table({"a": [1, 2, 3]})
     with pa.BufferOutputStream() as out:
         pq.write_table(table, out)
         buf = out.getvalue()
 
     original_metadata = pq.read_metadata(pa.BufferReader(buf))
+    row_group = original_metadata.row_group(0)
+    column_chunk = row_group.column(0)
+    metadata = {
+        "file": original_metadata,
+        "row_group": row_group,
+        "column_chunk": column_chunk,
+        "statistics": column_chunk.statistics,
+        "schema": original_metadata.schema,
+        "column_schema": original_metadata.schema.column(0),
+    }[kind]
+
+    assert metadata.equals(metadata)
+    assert operator.eq(metadata, metadata)
+    assert not operator.eq(metadata, None)
+    assert not operator.eq(None, metadata)
+    assert operator.ne(metadata, None)
+    assert operator.ne(None, metadata)
     match = "Argument 'other' has incorrect type"
     with pytest.raises(TypeError, match=match):
-        original_metadata.equals(None)
+        metadata.equals(None)
 
 
 @pytest.mark.parametrize("t1,t2,expected_error", (