我喜欢joctee的回答，因为它很简单。
if hasattr(request.user, 'type1profile'):
# do something
elif hasattr(request.user, 'type2profile'):
# do something else
else:
# do something else
其他评论者担心它可能不适用于某些版本的 Python 或 Django，但Django 文档将此技术显示为选项之一：
您还可以使用 hasattr 来避免异常捕获：
>>> hasattr(p2, 'restaurant')
False
当然，文档还显示了异常捕获技术：
p2 没有关联的餐厅：
>>> from django.core.exceptions import ObjectDoesNotExist
>>> try:
>>> p2.restaurant
>>> except ObjectDoesNotExist:
>>> print("There is no restaurant here.")
There is no restaurant here.
我同意Joshua的观点，即捕获异常可以更清楚地了解正在发生的事情，但对我来说似乎更混乱。也许这是一个合理的妥协？
>>> print(Restaurant.objects.filter(place=p2).first())
None
这只是Restaurant按位置查询对象。None如果那个地方没有餐厅，它会返回。
这是一个可执行代码片段，供您使用这些选项。如果你安装了 Python、Django 和 SQLite3，它应该可以运行。我用 Python 3.8.10 和 Django 4.0.2 对其进行了测试。
""" Django models in a single, runnable file.
Based on Nsukami's blog post: https://nskm.xyz/posts/dsfp/
To get it running, copy it into a directory named udjango:
$ pip install django
$ python udjango_models.py
Tested with Django 4.0 and Python 3.8.
"""
import logging
import sys
import django
from django.apps import apps
from django.apps.config import AppConfig
from django.conf import settings
from django.core.exceptions import ObjectDoesNotExist
from django.db import connections, models, DEFAULT_DB_ALIAS
from django.db.models.base import ModelBase
NAME = 'udjango'
DB_FILE = NAME + '.db'
def main():
setup()
class Place(models.Model):
name = models.CharField(max_length=50)
address = models.CharField(max_length=80)
def __str__(self):
return "%s the place" % self.name
class Restaurant(models.Model):
place = models.OneToOneField(Place, on_delete=models.CASCADE, primary_key=True)
serves_hot_dogs = models.BooleanField(default=False)
serves_pizza = models.BooleanField(default=False)
def __str__(self):
return "%s the restaurant" % self.place.name
class Waiter(models.Model):
restaurant = models.ForeignKey(Restaurant, on_delete=models.CASCADE)
name = models.CharField(max_length=50)
def __str__(self):
return "%s the waiter at %s" % (self.name, self.restaurant)
syncdb(Place)
syncdb(Restaurant)
syncdb(Waiter)
p1 = Place(name='Demon Dogs', address='944 W. Fullerton')
p1.save()
p2 = Place(name='Ace Hardware', address='1013 N. Ashland')
p2.save()
r = Restaurant(place=p1, serves_hot_dogs=True, serves_pizza=False)
r.save()
print(r.place)
print(p1.restaurant)
# Option 1: try/except
try:
print(p2.restaurant)
except ObjectDoesNotExist:
print("There is no restaurant here.")
# Option 2: getattr and hasattr
print(getattr(p2, 'restaurant', 'There is no restaurant attribute.'))
if hasattr(p2, 'restaurant'):
print('Restaurant found by hasattr().')
else:
print('Restaurant not found by hasattr().')
# Option 3: a query
print(Restaurant.objects.filter(place=p2).first())
def setup():
with open(DB_FILE, 'w'):
pass # wipe the database
settings.configure(
DEBUG=True,
DATABASES={
DEFAULT_DB_ALIAS: {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': DB_FILE}},
LOGGING={'version': 1,
'disable_existing_loggers': False,
'formatters': {
'debug': {
'format': '%(asctime)s[%(levelname)s]'
'%(name)s.%(funcName)s(): %(message)s',
'datefmt': '%Y-%m-%d %H:%M:%S'}},
'handlers': {
'console': {
'level': 'DEBUG',
'class': 'logging.StreamHandler',
'formatter': 'debug'}},
'root': {
'handlers': ['console'],
'level': 'WARN'},
'loggers': {
"django.db": {"level": "WARN"}}})
app_config = AppConfig(NAME, sys.modules['__main__'])
apps.populate([app_config])
django.setup()
original_new_func = ModelBase.__new__
@staticmethod
def patched_new(cls, name, bases, attrs):
if 'Meta' not in attrs:
class Meta:
app_label = NAME
attrs['Meta'] = Meta
return original_new_func(cls, name, bases, attrs)
ModelBase.__new__ = patched_new
def syncdb(model):
""" Standard syncdb expects models to be in reliable locations.
Based on https://github.com/django/django/blob/1.9.3
/django/core/management/commands/migrate.py#L285
"""
connection = connections[DEFAULT_DB_ALIAS]
with connection.schema_editor() as editor:
editor.create_model(model)
main()