Description

osamakader

opened on Oct 25, 2025

Issue body actions

Feature or enhancement

Proposal:

Description

The iterparse() function in xml.etree.ElementTree has a TODO comment (line 1270) requesting that a ResourceWarning be emitted when the iterator is garbage collected without being explicitly closed:

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()

The close() method has been available for many years now, so this TODO can be implemented.

Problem

When iterparse() opens a file by filename (rather than accepting a pre-opened file object), it manages the file internally. If the iterator is not explicitly closed, the file handle remains open until garbage collection, which can lead to:

• File descriptor leaks
• Files remaining locked on Windows
• Resource exhaustion in long-running programs

Currently, no warning is issued to alert developers of this problem.

Proposed Solution

Implement the TODO by:

1. Adding a _closed flag to track whether close() has been called
2. Emitting a ResourceWarning in __del__() if the iterator was not closed and had opened a file internally (close_source == True)
3. The warning should only apply when iterparse() opened the file itself (filename passed), not when a file object was provided

Example

Current behavior (no warning):

import xml.etree.ElementTree as ET

# This leaks a file handle but gives no warning
context = ET.iterparse('data.xml')
next(context)
# Iterator goes out of scope without close()

Expected behavior (with fix):

import xml.etree.ElementTree as ET

# This should emit ResourceWarning
context = ET.iterparse('data.xml')
next(context)
# ResourceWarning: unclosed file <_io.BufferedReader name='data.xml'>

# Proper usage (no warning):
context = ET.iterparse('data.xml')
next(context)
context.close()  # Explicit close

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-140601: Add ResourceWarning to iterparse when not closed #140603
• gh-140601: Refactor ElementTree.iterparse() tests #141499
• [3.14] gh-140601: Refactor ElementTree.iterparse() tests (GH-141499) #141502
• [3.13] gh-140601: Refactor ElementTree.iterparse() tests (GH-141499) #141503

Activity

1. osamakader

   added

   type-featureA feature request or enhancementA feature request or enhancement

   on Oct 25, 2025
2. osamakader

   added 5 commits that reference this issue on Oct 25, 2025

   pythongh-140601: Add ResourceWarning to iterparse when not closed

   e9cdee7

   pythongh-140601: Add ResourceWarning to iterparse when not closed

   a9e15e5

   pythongh-140601: Add ResourceWarning to iterparse when not closed

   b5c76da

   pythongh-140601: Add ResourceWarning to iterparse when not closed

   ad2354b

   pythongh-140601: Add ResourceWarning to iterparse when not closed

   7d1d79a
3. picnixz

   added

   topic-XML

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   on Oct 25, 2025
4. osamakader

   added 2 commits that reference this issue on Oct 25, 2025

   pythongh-140601: Add ResourceWarning to iterparse when not closed

   54742a1

   pythongh-140601: Add ResourceWarning to iterparse when not closed

   bf3f888
5. serhiy-storchaka

   added 2 commits that reference this issue on Nov 13, 2025

   pythongh-140601: Refactor ElementTree.iterparse() tests

   3b35a2c

   gh-140601: Refactor ElementTree.iterparse() tests (GH-141499)

   2fbd396
6. miss-islington

   added 2 commits that reference this issue on Nov 13, 2025

   pythongh-140601: Refactor ElementTree.iterparse() tests (pythonGH-141499

   75c5add

   pythongh-140601: Refactor ElementTree.iterparse() tests (pythonGH-141499

   f9570d7
7. serhiy-storchaka

   added 3 commits that reference this issue on Nov 13, 2025

   [3.13] gh-140601: Refactor ElementTree.iterparse() tests (GH-141499) (G…

   72b6ff0

   [3.14] gh-140601: Refactor ElementTree.iterparse() tests (GH-141499) (G…

   7b8c257

   gh-140601: Add ResourceWarning to iterparse when not closed (GH-140603)

   a486d45
8. serhiy-storchaka commented on Nov 13, 2025

   

   serhiy-storchaka

   on Nov 13, 2025

   Member

   More actions

   Thank you for your contribution @osamakader.
9. serhiy-storchaka

   closed this as completedon Nov 13, 2025
10. osamakader commented on Nov 13, 2025

    

    osamakader

    on Nov 13, 2025

    ContributorAuthor

    More actions

    Many thanks @serhiy-storchaka for your support.
11. CuriousLearner

    added 3 commits that reference this issue on Nov 13, 2025

    Merge branch 'main' into fix-issue21914

    b9f473c

    Merge branch 'main' of github.com:python/cpython into fix-Issue18387

    c46ecc5

    Merge branch 'main' of github.com:python/cpython into fix-issue24255

    c240289
12. StanFromIreland

    added 2 commits that reference this issue on Dec 6, 2025

    pythongh-140601: Refactor ElementTree.iterparse() tests (pythonGH-141499

    62a94d2

    pythongh-140601: Add ResourceWarning to iterparse when not closed (py…

    50f2e4e
13. fedepell

    added 3 commits that reference this issue on Dec 23, 2025

    Fix unit test with Python 3.15.0a3

    66566c9

    Fix unit test with Python 3.15.0a3

    9ea9fa3

    Fix unit test with Python 3.15.0a3

    c886729

Issue actions