Django 面试题集
Django Web 框架核心知识点与高频面试题
A. 面试宝典
基础题
1. Django MTV 架构
┌─────────────────────────────────────────────────────┐
│ Django MTV │
├─────────────────────────────────────────────────────┤
│ │
│ URL ──→ View ──→ Model ──→ Database │
│ │ │ │
│ └───→ Template ←─────┘ │
│ │ │
│ ↓ │
│ Response │
│ │
└─────────────────────────────────────────────────────┘| 组件 | 说明 | 对应 MVC |
|---|---|---|
| Model | 数据模型，ORM | Model |
| Template | 模板，HTML 渲染 | View |
| View | 视图，业务逻辑 | Controller |
python
# models.py
from django.db import models
class User(models.Model):
username = models.CharField(max_length=100, unique=True)
email = models.EmailField()
created_at = models.DateTimeField(auto_now_add=True)
class Meta:
db_table = 'users'
ordering = ['-created_at']
# views.py
from django.shortcuts import render, get_object_or_404
from django.http import JsonResponse
def user_list(request):
users = User.objects.all()
return render(request, 'users/list.html', {'users': users})
def user_detail(request, pk):
user = get_object_or_404(User, pk=pk)
return JsonResponse({'id': user.id, 'username': user.username})
# urls.py
from django.urls import path
from . import views
urlpatterns = [
path('users/', views.user_list, name='user_list'),
path('users/<int:pk>/', views.user_detail, name='user_detail'),
]2. ORM 查询
python
from django.db.models import Q, F, Count, Sum, Avg
# 基础查询
User.objects.all()
User.objects.get(pk=1)
User.objects.filter(age__gte=18)
User.objects.exclude(status='inactive')
User.objects.first()
User.objects.last()
User.objects.count()
User.objects.exists()
# 字段查找
User.objects.filter(name__exact='Tom')
User.objects.filter(name__iexact='tom') # 不区分大小写
User.objects.filter(name__contains='om')
User.objects.filter(name__icontains='om')
User.objects.filter(name__startswith='T')
User.objects.filter(name__endswith='m')
User.objects.filter(age__in=[18, 20, 22])
User.objects.filter(age__range=(18, 30))
User.objects.filter(email__isnull=True)
# 日期查询
User.objects.filter(created_at__year=2024)
User.objects.filter(created_at__month=1)
User.objects.filter(created_at__date=date.today())
# Q 对象（复杂查询）
User.objects.filter(Q(age__gte=18) | Q(status='vip'))
User.objects.filter(Q(age__gte=18) & ~Q(status='banned'))
# F 对象（字段引用）
User.objects.filter(updated_at__gt=F('created_at'))
User.objects.update(views=F('views') + 1)
# 聚合
User.objects.aggregate(
total=Count('id'),
avg_age=Avg('age'),
sum_balance=Sum('balance')
)
# 分组
User.objects.values('department').annotate(
count=Count('id'),
avg_age=Avg('age')
)
# 排序
User.objects.order_by('created_at')
User.objects.order_by('-created_at') # 降序
User.objects.order_by('department', '-age')
# 分页
User.objects.all()[10:20] # OFFSET 10 LIMIT 10
# 选择字段
User.objects.values('id', 'username')
User.objects.values_list('id', 'username')
User.objects.values_list('id', flat=True)
# 去重
User.objects.values('department').distinct()
# 关联查询
User.objects.select_related('profile') # 一对一/多对一
User.objects.prefetch_related('posts') # 一对多/多对多
# 原生 SQL
User.objects.raw('SELECT * FROM users WHERE age > %s', [18])
from django.db import connection
with connection.cursor() as cursor:
cursor.execute('SELECT * FROM users')
rows = cursor.fetchall()3. 模型关系
python
# 一对多
class Post(models.Model):
author = models.ForeignKey(
User,
on_delete=models.CASCADE,
related_name='posts'
)
title = models.CharField(max_length=200)
# 使用
user.posts.all()
post.author
# 多对多
class Tag(models.Model):
name = models.CharField(max_length=50)
class Article(models.Model):
tags = models.ManyToManyField(Tag, related_name='articles')
# 使用
article.tags.all()
article.tags.add(tag)
article.tags.remove(tag)
article.tags.set([tag1, tag2])
article.tags.clear()
# 一对一
class Profile(models.Model):
user = models.OneToOneField(
User,
on_delete=models.CASCADE,
related_name='profile'
)
avatar = models.ImageField(upload_to='avatars/')
# on_delete 选项
# CASCADE - 级联删除
# PROTECT - 阻止删除
# SET_NULL - 设为 NULL
# SET_DEFAULT - 设为默认值
# DO_NOTHING - 不做任何操作4. 类视图 (CBV)
python
from django.views import View
from django.views.generic import (
ListView, DetailView, CreateView, UpdateView, DeleteView
)
# 基础类视图
class UserView(View):
def get(self, request):
users = User.objects.all()
return JsonResponse({'users': list(users.values())})
def post(self, request):
data = json.loads(request.body)
user = User.objects.create(**data)
return JsonResponse({'id': user.id}, status=201)
# 通用视图
class UserListView(ListView):
model = User
template_name = 'users/list.html'
context_object_name = 'users'
paginate_by = 10
def get_queryset(self):
queryset = super().get_queryset()
name = self.request.GET.get('name')
if name:
queryset = queryset.filter(name__icontains=name)
return queryset
class UserDetailView(DetailView):
model = User
template_name = 'users/detail.html'
class UserCreateView(CreateView):
model = User
fields = ['username', 'email']
template_name = 'users/form.html'
success_url = '/users/'
class UserUpdateView(UpdateView):
model = User
fields = ['username', 'email']
template_name = 'users/form.html'
class UserDeleteView(DeleteView):
model = User
success_url = '/users/'5. 中间件
python
# 函数式中间件
def simple_middleware(get_response):
def middleware(request):
# 请求处理前
print(f"Before: {request.path}")
response = get_response(request)
# 响应处理后
print(f"After: {response.status_code}")
return response
return middleware
# 类式中间件
class LoggingMiddleware:
def __init__(self, get_response):
self.get_response = get_response
def __call__(self, request):
# 请求处理前
start_time = time.time()
response = self.get_response(request)
# 响应处理后
duration = time.time() - start_time
print(f"{request.method} {request.path} - {duration:.3f}s")
return response
def process_view(self, request, view_func, view_args, view_kwargs):
# 视图调用前
pass
def process_exception(self, request, exception):
# 异常处理
pass
def process_template_response(self, request, response):
# 模板响应处理
return response
# settings.py
MIDDLEWARE = [
'django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'myapp.middleware.LoggingMiddleware', # 自定义中间件
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
]进阶题
6. Django REST Framework
python
# serializers.py
from rest_framework import serializers
class UserSerializer(serializers.ModelSerializer):
class Meta:
model = User
fields = ['id', 'username', 'email', 'created_at']
read_only_fields = ['id', 'created_at']
def validate_email(self, value):
if User.objects.filter(email=value).exists():
raise serializers.ValidationError("Email already exists")
return value
# views.py
from rest_framework import viewsets, status
from rest_framework.decorators import action
from rest_framework.response import Response
from rest_framework.permissions import IsAuthenticated
class UserViewSet(viewsets.ModelViewSet):
queryset = User.objects.all()
serializer_class = UserSerializer
permission_classes = [IsAuthenticated]
def get_queryset(self):
queryset = super().get_queryset()
name = self.request.query_params.get('name')
if name:
queryset = queryset.filter(name__icontains=name)
return queryset
@action(detail=True, methods=['post'])
def activate(self, request, pk=None):
user = self.get_object()
user.is_active = True
user.save()
return Response({'status': 'activated'})
# urls.py
from rest_framework.routers import DefaultRouter
router = DefaultRouter()
router.register('users', UserViewSet)
urlpatterns = router.urls7. 信号与缓存
python
# 信号
from django.db.models.signals import post_save, pre_delete
from django.dispatch import receiver
@receiver(post_save, sender=User)
def user_created(sender, instance, created, **kwargs):
if created:
Profile.objects.create(user=instance)
@receiver(pre_delete, sender=User)
def user_deleted(sender, instance, **kwargs):
# 清理操作
pass
# 缓存
from django.core.cache import cache
from django.views.decorators.cache import cache_page
# 低级缓存 API
cache.set('key', 'value', timeout=300)
value = cache.get('key', default=None)
cache.delete('key')
cache.clear()
# 视图缓存
@cache_page(60 * 15) # 15 分钟
def user_list(request):
pass
# 模板缓存
{% load cache %}
{% cache 300 sidebar request.user.id %}
... sidebar content ...
{% endcache %}
# settings.py
CACHES = {
'default': {
'BACKEND': 'django.core.cache.backends.redis.RedisCache',
'LOCATION': 'redis://127.0.0.1:6379/1',
}
}避坑指南
| 错误回答 | 正确理解 |
|---|---|
| "QuerySet 立即执行" | QuerySet 是惰性的，使用时才执行 |
| "ForeignKey 默认可为空" | 默认 NOT NULL，需显式 null=True |
| "select_related 用于多对多" | 多对多用 prefetch_related |
| "中间件顺序不重要" | 顺序很重要，影响执行流程 |
| "Django ORM 不支持事务" | 支持，使用 transaction.atomic() |
B. 实战文档
项目结构
myproject/
├── manage.py
├── requirements.txt
├── myproject/
│ ├── __init__.py
│ ├── settings/
│ │ ├── __init__.py
│ │ ├── base.py
│ │ ├── development.py
│ │ └── production.py
│ ├── urls.py
│ └── wsgi.py
├── apps/
│ ├── users/
│ │ ├── models.py
│ │ ├── views.py
│ │ ├── serializers.py
│ │ ├── urls.py
│ │ └── tests.py
│ └── posts/
├── templates/
├── static/
└── media/常用命令
bash
# 创建项目
django-admin startproject myproject
# 创建应用
python manage.py startapp myapp
# 迁移
python manage.py makemigrations
python manage.py migrate
# 创建超级用户
python manage.py createsuperuser
# 运行服务器
python manage.py runserver
# Shell
python manage.py shell
# 测试
python manage.py test
# 收集静态文件
python manage.py collectstatic