Python 如何在 Django 中默认判断单选按钮中的值

我写了一份表格范本.我使用小部件来制作单选按钮，并且我希望在html文件中呈现表单时，默认选中特定的单选按钮.

模型:

class Room(models.Model):
    class Meta:
    number =  models.PositiveSmallIntegerField()
    CATEGORIES = (
        ('Regular', 'Regular'),
        ('Executive', 'Executive'),
        ('Deluxe', 'Deluxe'),
    )
    category = models.CharField(max_length=9, choices=CATEGORIES, default='Regular')
    CAPACITY = (
        (1, '1'),
        (2, '2'),
        (3, '3'),
        (4, '4'),
    )
    capacity = models.PositiveSmallIntegerField(
        choices=CAPACITY, default=2
        )
    advance = models.PositiveSmallIntegerField(default=10)
    manager = models.CharField(max_length=30)

以下是基于上述模型的我的模型表单.

表格:

class AddRoomForm(forms.ModelForm):
    ROOM_CATEGORIES = (
        ('Regular', 'Regular'),
        ('Executive', 'Executive'),
        ('Deluxe', 'Deluxe'),
    )

    category = forms.CharField(
        max_length=9,
        widget=forms.RadioSelect(choices=ROOM_CATEGORIES),
    )

    ROOM_CAPACITY = (
        (1, '1'),
        (2, '2'),
        (3, '3'),
        (4, '4'),
    )

    capacity = forms.CharField(
        max_length=9,
        widget=forms.RadioSelect(choices=ROOM_CAPACITY),
    )
    class Meta:
        model = Room
        fields = ['number', 'category', 'capacity', 'advance']

以下是观点:

def add_room(request):
    if request. Method == 'POST':
        form = AddRoomForm(request.POST)
        if form.is_valid():
            room = Room(number=request.POST['number'],
                    category=request.POST['category'],
                    capacity=request.POST['capacity'],
                    advance=request.POST['advance'],
                    manager=request.user.username)
            room.save()
            # Implemented Post/Redirect/Get.
            return redirect('../rooms/')
        else:
            context = {
                'form': form,
                'username': request.user.username
                }
            return render(request, 'add_room.html', context)
    context = {
            'form': AddRoomForm(),
            'username': request.user.username
            }
    return render(request, 'add_room.html', context)

我在我的html文件中呈现了这样的表单.

<form method="POST">
  {% csrf_token %}
  {{ form.as_p }}
  <input type="submit" class= "submit submit-right" value="Add" />
</form>

我在某个地方读到，我可以在我的views.py文件中使用‘初始’关键字，但我不知道如何使用它.有没有人能帮我一下？