Django database query: How to get object by id?

问题

Django automatically creates an id field as primary key.

Now I need to get the object by this id.

object = Class.objects.filter() 

How to write this filter?

回答1:

If you want to get an object, using get() is more straightforward:

obj = Class.objects.get(pk=this_object_id)

回答2:

I got here for the same problem, but for a different reason:

Class.objects.get(id=1)

This code was raising an ImportError exception. What was confusing me was that the code below executed fine and returned a result set as expected:

Class.objects.all()

Tail of the traceback for the get() method:

File "django/db/models/loading.py", line 197, in get_models
    self._populate()
File "django/db/models/loading.py", line 72, in _populate
    self.load_app(app_name, True)
File "django/db/models/loading.py", line 94, in load_app
    app_module = import_module(app_name)
File "django/utils/importlib.py", line 35, in import_module
    __import__(name)
ImportError: No module named myapp

Reading the code inside Django's loading.py, I came to the conclusion that my settings.py had a bad path to my app which contains my Class model definition. All I had to do was correct the path to the app and the get() method executed fine.

Here is my settings.py with the corrected path:

INSTALLED_APPS = (
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.sites',
    # ...
    'mywebproject.myapp',

)

All the confusion was caused because I am using Django's ORM as a standalone, so the namespace had to reflect that.

回答3:

You can also do:

obj = ClassModel.get_by_id(object_id)

This works, but there may I'm not sure if it's supported in Django 2.

回答4:

You can use:

objects_all=Class.objects.filter(filter_condition="")

This will return a query set even if it gets one object. If you need exactly one object use:

obj=Class.objects.get(conditon="")

来源：https://stackoverflow.com/questions/4300365/django-database-query-how-to-get-object-by-id