NameError：在Django ORM查询中未定义名称“ F”

Question

I'm using the ipython (Python 3.7) console in PyCharm. I'm trying got run a Django ORM query

Article.objects.filter((round(datetime.now(timezone.utc) - F("created_on")) / 300) * 300)

but I'm getting the following error

Traceback (most recent call last):
  File "/Users/davea/Documents/workspace/mainpage_project/venv/lib/python3.7/site-packages/IPython/core/interactiveshell.py", line 3267, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-12-53618885441a>", line 1, in <module>
    Article.objects.filter((round(datetime.now(timezone.utc) - F("created_on")) / 300) * 300)
NameError: name 'F' is not defined

I thought "F" was the way to reference a field in my model in an expression but I get the error above. My Article model contains the field as below ...

class Article(models.Model):
    ...
    created_on = models.DateTimeField(default=datetime.now)

Answer 1

在Python控制台中，您需要导入F

from django.db.models import F