Regression Moving from Python 2 to Python 3

[speedplane]

I have recently started porting a code base from python 2 to 3, including dateutil. I've noticed there is a regression in behavior for some dates that are not perfectly formatted. In the examples below, it tries to parse 'Sep. 19,2013':

Python 2 Behavior

import dateutil.parser
dateutil.parser.parse('Sep. 19,2013')
> datetime.datetime(2013, 9, 19, 0, 0)

Python 3 Behavior

import dateutil.parser
dateutil.parser.parse('Sep. 19,2013')
> datetime.datetime(2020, 9, 19, 0, 0)

The Python 2 behavior appears to be more correct in this case. Is this type of imperfect date formatting supposed to be supported by dateutil? Any way to get the older behavior working in Python 3? We rely on some of this cleanup.

[ffe4]

I could not reproduce this issue. First of all, if I use your import pattern, I get an error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'dateutil' has no attribute 'parser'

If I use a working import pattern, I get the same result for both:

With python-dateutil==2.8.1 on Python 3.8.2

>>> from dateutil.parser import parse
>>> parse('Sep. 19,2013')
datetime.datetime(2020, 9, 19, 0, 0)

With python-dateutil==2.8.1 on Python 2.7.17

>>> from dateutil.parser import parse
>>> parse('Sep. 19,2013')
datetime.datetime(2020, 9, 19, 0, 0)

I also tried python-dateutil==2.5.0, with the same result.
Could you check your specific versions of both python and dateutil?

[speedplane]

Hi @ffe4,
Note: You're right about the import. The original import statements were working for me just because I had a built-in startup script that had imported dateutil.parser. I've edited the original issue.

However, the main issue remains the same. The original dateutil parser is very old, version 1.5.

For Python 2

• Python 2.7.18.
• dateutil version 1.5 (it's very old)

>>> from dateutil.parser import parse
>>> parse('Sep. 19,2013')
datetime.datetime(2013, 9, 19, 0, 0)

For Python 3

• Python 3.5.2
• dateutil version 2.8.1

In [7]: import dateutil.parser; dateutil.parser.parse('Sep. 19,2013')
Out[7]: datetime.datetime(2020, 9, 19, 0, 0)

[speedplane]

I can get it working in Python 3 if I install version 1.5 and run 2to3.

pip3 install --upgrade python-dateutil==1.5
2to3 -w /usr/local/lib/python3.5/dist-packages/dateutil/
python3
>>> from dateutil.parser import parse
>>> parse('Sep. 19,2013')
datetime.datetime(2013, 9, 19, 0, 0)

[pganssle]

So this is not related to Python 2 or 3, it's just a change that happened in the parsing logic. I would guess around 2.4-ish.

This is a duplicate of #939