gh-69893: Add the close() method for xml.etree.ElementTree.iterparse() iterator (GH-114534)

Author: serhiy-storchaka

Doc/library/xml.etree.elementtree.rst

@@ -625,6 +625,8 @@ Functions
    target. Returns an :term:`iterator` providing ``(event, elem)`` pairs;
    it has a ``root`` attribute that references the root element of the
    resulting XML tree once *source* is fully read.
+   The iterator has the :meth:`!close` method that closes the internal
+   file object if *source* is a filename.
 
    Note that while :func:`iterparse` builds the tree incrementally, it issues
    blocking reads on *source* (or the file it names).  As such, it's unsuitable
@@ -647,6 +649,9 @@ Functions
    .. versionchanged:: 3.8
       The ``comment`` and ``pi`` events were added.
 
+   .. versionchanged:: 3.13
+      Added the :meth:`!close` method.
+
 
 .. function:: parse(source, parser=None)
 

Doc/whatsnew/3.13.rst

@@ -472,6 +472,14 @@ warnings
   warning may also be emitted when a decorated function or class is used at runtime.
   See :pep:`702`. (Contributed by Jelle Zijlstra in :gh:`104003`.)
 
+xml.etree.ElementTree
+---------------------
+
+* Add the :meth:`!close` method for the iterator returned by
+  :func:`~xml.etree.ElementTree.iterparse` for explicit cleaning up.
+  (Contributed by Serhiy Storchaka in :gh:`69893`.)
+
+
 Optimizations
 =============
 

Lib/test/test_xml_etree.py

@@ -555,6 +555,17 @@ def test_iterparse(self):
                 ('end', '{namespace}root'),
             ])
 
+        with open(SIMPLE_XMLFILE, 'rb') as source:
+            context = iterparse(source)
+            action, elem = next(context)
+            self.assertEqual((action, elem.tag), ('end', 'element'))
+            self.assertEqual([(action, elem.tag) for action, elem in context], [
+                    ('end', 'element'),
+                    ('end', 'empty-element'),
+                    ('end', 'root'),
+                ])
+            self.assertEqual(context.root.tag, 'root')
+
         events = ()
         context = iterparse(SIMPLE_XMLFILE, events)
         self.assertEqual([(action, elem.tag) for action, elem in context], [])
@@ -646,12 +657,81 @@ def test_iterparse(self):
 
         # Not exhausting the iterator still closes the resource (bpo-43292)
         with warnings_helper.check_no_resource_warning(self):
-            it = iterparse(TESTFN)
+            it = iterparse(SIMPLE_XMLFILE)
             del it
 
+        with warnings_helper.check_no_resource_warning(self):
+            it = iterparse(SIMPLE_XMLFILE)
+            it.close()
+            del it
+
+        with warnings_helper.check_no_resource_warning(self):
+            it = iterparse(SIMPLE_XMLFILE)
+            action, elem = next(it)
+            self.assertEqual((action, elem.tag), ('end', 'element'))
+            del it, elem
+
+        with warnings_helper.check_no_resource_warning(self):
+            it = iterparse(SIMPLE_XMLFILE)
+            action, elem = next(it)
+            it.close()
+            self.assertEqual((action, elem.tag), ('end', 'element'))
+            del it, elem
+
         with self.assertRaises(FileNotFoundError):
             iterparse("nonexistent")
 
+    def test_iterparse_close(self):
+        iterparse = ET.iterparse
+
+        it = iterparse(SIMPLE_XMLFILE)
+        it.close()
+        with self.assertRaises(StopIteration):
+            next(it)
+        it.close()  # idempotent
+
+        with open(SIMPLE_XMLFILE, 'rb') as source:
+            it = iterparse(source)
+            it.close()
+            self.assertFalse(source.closed)
+            with self.assertRaises(StopIteration):
+                next(it)
+            it.close()  # idempotent
+
+        it = iterparse(SIMPLE_XMLFILE)
+        action, elem = next(it)
+        self.assertEqual((action, elem.tag), ('end', 'element'))
+        it.close()
+        with self.assertRaises(StopIteration):
+            next(it)
+        it.close()  # idempotent
+
+        with open(SIMPLE_XMLFILE, 'rb') as source:
+            it = iterparse(source)
+            action, elem = next(it)
+            self.assertEqual((action, elem.tag), ('end', 'element'))
+            it.close()
+            self.assertFalse(source.closed)
+            with self.assertRaises(StopIteration):
+                next(it)
+            it.close()  # idempotent
+
+        it = iterparse(SIMPLE_XMLFILE)
+        list(it)
+        it.close()
+        with self.assertRaises(StopIteration):
+            next(it)
+        it.close()  # idempotent
+
+        with open(SIMPLE_XMLFILE, 'rb') as source:
+            it = iterparse(source)
+            list(it)
+            it.close()
+            self.assertFalse(source.closed)
+            with self.assertRaises(StopIteration):
+                next(it)
+            it.close()  # idempotent
+
     def test_writefile(self):
         elem = ET.Element("tag")
         elem.text = "text"
@@ -3044,8 +3124,7 @@ def test_basic(self):
         # With an explicit parser too (issue #9708)
         sourcefile = serialize(doc, to_string=False)
         parser = ET.XMLParser(target=ET.TreeBuilder())
-        self.assertEqual(next(ET.iterparse(sourcefile, parser=parser))[0],
-                         'end')
+        self.assertEqual(next(ET.iterparse(sourcefile, parser=parser))[0], 'end')
 
         tree = ET.ElementTree(None)
         self.assertRaises(AttributeError, tree.iter)

Lib/xml/etree/ElementTree.py

@@ -1248,10 +1248,17 @@ def iterator(source):
             if close_source:
                 source.close()
 
+    gen = iterator(source)
     class IterParseIterator(collections.abc.Iterator):
-        __next__ = iterator(source).__next__
+        __next__ = gen.__next__
+        def close(self):
+            if close_source:
+                source.close()
+            gen.close()
 
         def __del__(self):
+            # TODO: Emit a ResourceWarning if it was not explicitly closed.
+            # (When the close() method will be supported in all maintained Python versions.)
             if close_source:
                 source.close()
 

Misc/NEWS.d/next/Library/2024-01-24-17-25-18.gh-issue-69893.PQq5fR.rst

@@ -0,0 +1,2 @@
+Add the :meth:`!close` method for the iterator returned by
+:func:`xml.etree.ElementTree.iterparse`.