New submission from Tim Bell:
Python 3.6 documentation for email.utils.parsedate_to_datetime() says "Performs
the same function as parsedate(), but on success returns a datetime." The docs
for parsedate() say "If it succeeds in parsing the date...; otherwise None will
be returned." By implication, parsedate_to_datetime() should return None when
the date can't be parsed.
There are two different failure modes for parsedate_to_datetime():
1. When _parsedate_tz() fails to parse the date and returns None:
>>> from email.utils import parsedate_to_datetime
>>> parsedate_to_datetime('0')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python3.6/email/utils.py", line 210, in parsedate_to_datetime
*dtuple, tz = _parsedate_tz(data)
TypeError: 'NoneType' object is not iterable
2. When _parsedate_tz() succeeds, but conversion to datetime.datetime fails:
>>> parsedate_to_datetime('Tue, 06 Jun 2017 27:39:33 +0600')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python3.6/email/utils.py", line 214, in parsedate_to_datetime
tzinfo=datetime.timezone(datetime.timedelta(seconds=tz)))
ValueError: hour must be in 0..23
Note that this second case is the one that led me to this issue. I am using the
email package to parse spam emails for subsequent analysis, and a certain group
of spam emails contain invalid hour fields in their Date header. I don't
require the invalid Date header to be converted to a datetime.datetime, but
accessing email_message['date'] to access the header value as a string triggers
the ValueError exception. I can work around this with a custom email policy,
but the observed behaviour does seem to contradict the documented behaviour.
Also, in relation to https://bugs.python.org/issue15925, r.david.murray
commented "Oh, and I'm purposely allowing parsedate_to_datetime throw
exceptions. I suppose that should be documented, but that's a separate issue."
However, no argument for why parsedate_to_datetime throwing exceptions is
desired was given.
----------
components: email
messages: 296137
nosy: barry, r.david.murray, timb07
priority: normal
severity: normal
status: open
title: email.utils.parsedate_to_datetime() should return None when date cannot
be parsed
type: behavior
versions: Python 3.5, Python 3.6
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue30681>
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