Filter with custom date class

Using Django Using the ORM
1

Hi,

I introduced a custom date class

CustomDate(datetime.date):
  pass

and found, that it isn’t recognized as date when I filter

MyModel.objects.filter(some_date_field=CustomDate.today())

Is this intentionally or is it a bug?

2

The date “object” in Python isn’t a standard class.

From inside a Python shell:

In [8]: import datetime

In [9]: type(datetime)
Out[9]: module

In [10]: type(datetime.datetime)
Out[10]: type

In [11]: type(datetime.datetime.date)
Out[11]: method_descriptor

In [13]: class CustomDatetime(datetime.datetime):
    ...:     pass
    ...: 

In [14]: CustomDatetime.today()
Out[14]: CustomDatetime(2024, 6, 27, 11, 56, 21, 678109)

In [15]: type(CustomDatetime.today())
Out[15]: __main__.CustomDatetime

In [16]: User.objects.filter(last_login=CustomDatetime.today())
/home/tskww/ve/d5-c4/lib/python3.12/site-packages/django/db/models/fields/__init__.py:1659: RuntimeWarning: DateTimeField User.last_login received a naive datetime (2024-06-27 11:57:30.531250) while time zone support is active.
  warnings.warn(
Out[16]: <QuerySet []>

In [17]: class CustomDate(datetime.datetime.date):
    ...:     pass
    ...: 
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[17], line 1
----> 1 class CustomDate(datetime.datetime.date):
      2     pass

TypeError: cannot create 'method_descriptor' instances

In [18]: from datetime import datetime

In [19]: class CustomDate(datetime.date):
    ...:     pass
    ...: 
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[19], line 1
----> 1 class CustomDate(datetime.date):
      2     pass

TypeError: cannot create 'method_descriptor' instances

In [20]: class CustomDate(datetime):
    ...:     pass
    ...: 

In [21]: User.objects.filter(last_login=CustomDate.today())
/home/tskww/ve/d5-c4/lib/python3.12/site-packages/django/db/models/fields/__init__.py:1659: RuntimeWarning: DateTimeField User.last_login received a naive datetime (2024-06-27 12:00:06.348283) while time zone support is active.
  warnings.warn(
Out[21]: <QuerySet []>

Second session, after logging in to the website:

In [1]: from datetime import datetime

In [2]: class CustomDate(datetime):
   ...:     pass
   ...: 

In [3]: User.objects.filter(last_login__date=CustomDate.today().date())
Out[3]: <QuerySet [<User: tskww>]>
3

Hi @KenWhitesell thanks for the quick response and I’m very sorry for wasting your time …

I actually did use the date type (and not the date method of the datetime class) …

In my more complex code this didn’t work … but in the simple test case I wrote now, it works as expected … :man_facepalming:

I may need to dig deeper to understand what’s wrong.

4

Ahh … I found the issue. My “simple” test case was too simple.

My CustomDate class looks actually like this:

from datetime import date

class CustomDate(date):
    def __str__(self) -> str:
        return self.strftime("%Y%m%d")

This is a bit surprising … but hey … a lot of magic happens in django :smiley: