Hello Guiseppe,
django.utils.dateparse provides helpers needed by Django to implement datetime,
date and time fields on SQLite. (SQLite doesn't have a native date time type.)
Their job is to parse ISO 8601 fast. That's it.
A utility module should do exactly what Django needs and nothing more.
django.utils.dateparse is documented so you can use it if it does what you
want. If it doesn't, use something else ;-)
Django forms try various formats when they receive user input because there's
uncertainty about the format. If you're parsing user input, then you should use
a form and you'll get the behavior you want.
To clarify my point about performance, here's the function you're proposing,
minus support for USE_L10N:
def parse_datetime_alternative(value):
for format in settings.DATETIME_INPUT_FORMATS:
try:
return datetime.datetime.strptime(format, value)
except (ValueError, TypeError):
continue
It's 10 times slower than the current implementation of parse_datetime:
$ python -m timeit -s "from django.conf import settings; settings.configured or
settings.configure(); from django.utils.dateparse import
parse_datetime_alternative as parse_datetime"
"parse_datetime('2019-02-03T17:27:58.645194')"
5000 loops, best of 5: 54.2 usec per loop
$ python -m timeit -s "from django.utils.dateparse import parse_datetime"
"parse_datetime('2019-02-03T17:27:58.645194')"
50000 loops, best of 5: 5.48 usec per loop
I implemented parse_datetime with a regex because that's almost twice as fast
as a single call to datetime.datetime.strptime:
$ python -m timeit -s "import datetime"
"datetime.datetime.strptime('2019-02-03T17:27:58.645194',
'%Y-%m-%dT%H:%M:%S.%f')"
20000 loops, best of 5: 9.87 usec per loop
Best regards,
--
Aymeric.
> On 3 Feb 2019, at 17:10, Giuseppe De Marco <giuseppe.dema...@unical.it> wrote:
>
> Hi All, it's the first time for me in this ml,
>
> I'd like to purpose a refactor of django.utils.dateparse functions.
> Currently a function in it, like parse_date for example, extract date time
> string with a static regexp...
>
> https://docs.djangoproject.com/pl/2.1/_modules/django/utils/dateparse/
> <https://docs.djangoproject.com/pl/2.1/_modules/django/utils/dateparse/>
>
> The first time I used It I thought that those functions parses date, time and
> date time, according to settings.py definitions like DATETIME_INPUT_FORMATS,
> but It was not this way... Then I read the code.
>
> Wouldn't It better to use settings.py definitions to manage these formats and
> django.utils.dateparse behaviour?
>
>
>
>
> --
> You received this message because you are subscribed to the Google Groups
> "Django developers (Contributions to Django itself)" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to django-developers+unsubscr...@googlegroups.com
> <mailto:django-developers+unsubscr...@googlegroups.com>.
> To post to this group, send email to django-developers@googlegroups.com
> <mailto:django-developers@googlegroups.com>.
> Visit this group at https://groups.google.com/group/django-developers
> <https://groups.google.com/group/django-developers>.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/django-developers/CABms%2BYpGtCQ1yzVfGtRKpDv60-4oH_SyGpPQYR6j1cR%2BL5LFRA%40mail.gmail.com
>
> <https://groups.google.com/d/msgid/django-developers/CABms%2BYpGtCQ1yzVfGtRKpDv60-4oH_SyGpPQYR6j1cR%2BL5LFRA%40mail.gmail.com?utm_medium=email&utm_source=footer>.
> For more options, visit https://groups.google.com/d/optout
> <https://groups.google.com/d/optout>.
--
You received this message because you are subscribed to the Google Groups
"Django developers (Contributions to Django itself)" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to django-developers+unsubscr...@googlegroups.com.
To post to this group, send email to django-developers@googlegroups.com.
Visit this group at https://groups.google.com/group/django-developers.
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-developers/BEAAEDB4-D58E-4CD0-8F1A-11A5F60B556B%40polytechnique.org.
For more options, visit https://groups.google.com/d/optout.
