commit 04f6fbb6969e9860783b9ab4dc24b6fe3c6dab8d
author Noor Michael <nsmichael31@gmail.com> Wed Mar 03 10:58:57 2021 -0600
committer GitHub <noreply@github.com> Wed Mar 03 08:58:57 2021 -0800
tree 7f6d18531f446b876b2f375f1a341a18a2a56775
parent 3b4b2cf418707c79f96689e401e3c703c0fdd4d2

bpo-43295: Fix error handling of datetime.strptime format string '%z' (GH-24627)



Previously, `datetime.strptime` would match `'z'` with the format string `'%z'` (for UTC offsets), throwing an `IndexError` by erroneously trying to parse `'z'` as a timestamp. As a special case, `'%z'` matches the string `'Z'` which is equivalent to the offset `'+00:00'`, however this behavior is not defined for lowercase `'z'`.

This change ensures a `ValueError` is thrown when encountering the original example, as follows:

```
>>> from datetime import datetime
>>> datetime.strptime('z', '%z')
ValueError: time data 'z' does not match format '%z'
```

Automerge-Triggered-By: GH:pganssle

Lib/_strptime.py

diff --git a/Lib/_strptime.py b/Lib/_strptime.py
index 5df37f5..b97dfcc 100644
--- a/Lib/_strptime.py
+++ b/Lib/_strptime.py
@@ -201,7 +201,7 @@ def __init__(self, locale_time=None):
             #XXX: Does 'Y' need to worry about having less or more than
             #     4 digits?
             'Y': r"(?P<Y>\d\d\d\d)",
-            'z': r"(?P<z>[+-]\d\d:?[0-5]\d(:?[0-5]\d(\.\d{1,6})?)?|Z)",
+            'z': r"(?P<z>[+-]\d\d:?[0-5]\d(:?[0-5]\d(\.\d{1,6})?)?|(?-i:Z))",
             'A': self.__seqToRE(self.locale_time.f_weekday, 'A'),
             'a': self.__seqToRE(self.locale_time.a_weekday, 'a'),
             'B': self.__seqToRE(self.locale_time.f_month[1:], 'B'),