在用户选择Django表单中的汽车品牌后，显示一组汽车模型

# forms.py
from django import forms

class CarForm(forms.Form):
    brand_choices = (
        ('bmw', 'BMW'),
        ('audi', 'Audi'),
        ('mercedes', 'Mercedes'),
    )
    model_choices = (
        ('x5', 'X5'),
        ('a4', 'A4'),
        ('c-class', 'C-Class'),
    )
    brand = forms.ChoiceField(choices=brand_choices)
    models = forms.MultipleChoiceField(choices=model_choices)

# views.py
from django.shortcuts import render
from .forms import CarForm

def car_form_view(request):
    if request.method == 'POST':
        form = CarForm(request.POST)
        if form.is_valid():
            brand = form.cleaned_data['brand']
            # Query the database to get car models based on the selected brand
            # For example:
            if brand == 'bmw':
                models = ['X5', 'X3', 'X1']
            elif brand == 'audi':
                models = ['A4', 'A6', 'Q5']
            elif brand == 'mercedes':
                models = ['C-Class', 'E-Class', 'S-Class']
            else:
                models = []
            return render(request, 'car_form.html', {'form': form, 'models': models})
    else:
        form = CarForm()
    return render(request, 'car_form.html', {'form': form})

# car_form.html
<form method="post">
    {% csrf_token %}
    {{ form.as_p }}
    <input type="submit" value="Submit">
</form>

{% if models %}
    <h3>Available Car Models:</h3>
    <ul>
        {% for model in models %}
            <li>{{ model }}</li>
        {% endfor %}
    </ul>
{% endif %}