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gh-151221: Fix plistlib loading of partial ISO 8601 dates #151217

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gh-151221: Fix plistlib loading of partial ISO 8601 dates #151217

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d549737
Fix plistlib loading of partial ISO 8601 dates
JavaZeroo Jun 10, 2026
526bbb5
Add NEWS entry
JavaZeroo Jun 10, 2026
c0c74b2
Document the behaviour change in plistlib docs
JavaZeroo Jun 10, 2026
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5 changes: 5 additions & 0 deletions Doc/library/plistlib.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -81,6 +81,11 @@ This module defines the following functions:
.. versionchanged:: 3.13
The keyword-only parameter *aware_datetime* has been added.

.. versionchanged:: next
``<date>`` values that omit smaller units (for example ``2024-06Z``)
are now accepted, with the omitted components defaulting to the start
of the period. Previously such values raised :exc:`TypeError`.


.. function:: loads(data, *, fmt=None, dict_type=dict, aware_datetime=False)

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10 changes: 4 additions & 6 deletions Lib/plistlib.py
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Expand Up @@ -139,13 +139,11 @@ def _decode_base64(s):

def _date_from_string(s, aware_datetime):
order = ('year', 'month', 'day', 'hour', 'minute', 'second')
# Smaller units may be omitted; default them to the start of the period.
defaults = (1, 1, 1, 0, 0, 0)
gd = _dateParser.match(s).groupdict()
lst = []
for key in order:
val = gd[key]
if val is None:
break
lst.append(int(val))
lst = [int(val) if (val := gd[key]) is not None else default
for key, default in zip(order, defaults)]
if aware_datetime:
return datetime.datetime(*lst, tzinfo=datetime.UTC)
return datetime.datetime(*lst)
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18 changes: 18 additions & 0 deletions Lib/test/test_plistlib.py
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Expand Up @@ -938,6 +938,24 @@ def test_load_aware_datetime(self):
aware_datetime=True)
self.assertEqual(dt.tzinfo, datetime.UTC)

def test_load_partial_datetime(self):
# Smaller units may be omitted; missing components default to the
# start of the period.
for data, expected in [
(b"<plist><date>2024Z</date></plist>",

@AleksaMCode AleksaMCode Jun 10, 2026

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I'm not sure if 2024Z is a valid ISO 8601 format. While year only (YYYY) format is ISO, I think timezone designators (in this case Zulu time) can only be attached to complete time value, not a standalone year.

@JavaZeroo JavaZeroo Jun 10, 2026

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You're right, Z only belongs on a full time value, so 2024Z isn't strictly valid ISO 8601. Whether to accept partial dates at all is still being discussed in the issue. If accepted, I'll drop the Z from the examples.

datetime.datetime(2024, 1, 1)),
(b"<plist><date>2024-06Z</date></plist>",
datetime.datetime(2024, 6, 1)),
(b"<plist><date>2024-06-07Z</date></plist>",
datetime.datetime(2024, 6, 7)),
(b"<plist><date>2024-06-07T08Z</date></plist>",
datetime.datetime(2024, 6, 7, 8)),
(b"<plist><date>2024-06-07T08:09Z</date></plist>",
datetime.datetime(2024, 6, 7, 8, 9)),
]:
with self.subTest(data=data):
self.assertEqual(plistlib.loads(data), expected)

@unittest.skipUnless("America/Los_Angeles" in zoneinfo.available_timezones(),
"Can't find timezone datebase")
def test_dump_aware_datetime(self):
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2026-06-10-06-36-35.gh-issue-151221.DPeEZr.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix :mod:`plistlib` raising a confusing :exc:`TypeError` when loading a
``<date>`` that omits smaller units (for example ``2024-06Z`` or ``2024Z``).
The omitted components now default to the start of the period.
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