在Django中保存ModelForm后获取主键

from django.http import HttpResponseRedirect
from django.shortcuts import render
from .models import MyModel
from .forms import MyModelForm

def create_view(request):
    if request.method == 'POST':
        form = MyModelForm(request.POST)
        if form.is_valid():
            my_model = form.save()
            # 获取主键
            primary_key = my_model.pk
            return HttpResponseRedirect('/success/')
    else:
        form = MyModelForm()
    return render(request, 'create.html', {'form': form})