Python学习笔记

首先电脑要安装python解释器,mysql软件（一般都是安装MariaDB）

1. 安装 Django

如果你还没有安装 Django，可以通过以下命令安装：

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pip install django

2. 创建一个新的 Django 项目

如果你还没有一个 Django 项目，可以使用以下命令创建一个：

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django-admin startproject myproject

这将创建一个名为 myproject 的目录，其中包含一个基本的 Django 项目结构。

进入项目目录：

bash 复制代码

cd myproject

3. 创建一个新的应用

在项目目录中，运行以下命令来创建一个新的应用：

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python manage.py startapp myapp

这将创建一个名为 myapp 的目录，其中包含以下文件结构：

4. 然后运行下面的命令

bash 复制代码

# 创建自己本地的命名空间（作用：会把项目里面使用到的软件都会下载在本地的命名空间里面，不会污染电脑环境的其他软件
1、python -m venv myvenv 
2、source myvenv/bin/activate
# 这个是下载项目里面使用的依赖，相当于js里面的package.json 
3、pip install -r ./requirement.txt 
4、python manage.py makemigrations
5、python manage.py migrate
6、python manage.py runserver
7、pip freeze > requirements.txt 
# 这个是国内的镜像下载速度会比较快 这个配置一般放在requirement.txt文件的第一行
8、-i https://pypi.doubanio.com/simple  
9、python manage.py startapp car

5. 在myproject里面配置

markdown 复制代码

├── asgi.py
├── __init__.py
├── settings.py
├── urls.py
└── wsgi.py

5.1 urls.py文件

这个文件一般配置当先项目里面所有的应用的路径，每一个应用都是一个单独的模块,比如path('/user', include('car.urls'))里面的/user就表示这个是用户模块，Car.urls后面所有的路径就都会带user这个前缀

javascript 复制代码

from django.contrib import admin
from django.urls import path, include
urlpatterns = [
    path('/user', include('car.urls')),
]

5.2 settings.py文件

ini 复制代码

"""
Django settings for Python_study project.

Generated by 'django-admin startproject' using Django 4.2.20.

For more information on this file, see
https://docs.djangoproject.com/en/4.2/topics/settings/

For the full list of settings and their values, see
https://docs.djangoproject.com/en/4.2/ref/settings/
"""

from pathlib import Path

# Build paths inside the project like this: BASE_DIR / 'subdir'.
BASE_DIR = Path(__file__).resolve().parent.parent


# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/4.2/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = 'django-insecure-3ef$zg2vf##&f2xmheo-&_@)vouf@x#oawzp%^lt5b3*pml^d6'

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = True

ALLOWED_HOSTS = []


# Application definition

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'car.apps.CarConfig',  # 在外面创建的每一个应用都在这里注册一下
]

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]
# 这个名字也可以修改，要和外面的东西保持一致就行
ROOT_URLCONF = 'Python_study.urls'

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]
# 这个名字也可以修改，要和外面的东西保持一致就行
WSGI_APPLICATION = 'Python_study.wsgi.application'


# Database
# https://docs.djangoproject.com/en/4.2/ref/settings/#databases

# DATABASES = {
#     'default': {
#         'ENGINE': 'django.db.backends.sqlite3',
#         'NAME': BASE_DIR / 'db.sqlite3',
#     }
# }

DATABASES = {
    'default': {
    'ENGINE': 'django.db.backends.mysql',  # 自动去连接mysql
    'NAME':'new_guozhixiong_db',           # 数据库名称
    'USER': 'root',                        # 数据库用户名
    'PASSWORD': 'Guoyu@657',               # 数据库密码
    'HOST': '127.0.0.1',                   # 数据库地址
    'PORT': 3306,                          # 数据库端口
    }
}


# Password validation
# https://docs.djangoproject.com/en/4.2/ref/settings/#auth-password-validators

AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
    },
]


# Internationalization
# https://docs.djangoproject.com/en/4.2/topics/i18n/

LANGUAGE_CODE = 'en-us'

TIME_ZONE = 'UTC'

USE_I18N = True

USE_TZ = True


# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/4.2/howto/static-files/

STATIC_URL = 'static/'

# Default primary key field type
# https://docs.djangoproject.com/en/4.2/ref/settings/#default-auto-field

DEFAULT_AUTO_FIELD = 'django.db.models.BigAutoField'

5.3 其余的文件暂时可以不用考虑

...

6 单独创建的应用

6.1 文件结构

bash 复制代码

├── admin.py   # 这个文件忽略一把不会修改这个文件
├── apps.py
├── __init__.py
├── migrations
├── models.py
├── pagination.py   # 这个是封装的方法
├── serializers.py  # 这个是封装的方法
├── tests.py        # 这个不用考虑
├── urls.py        
└── views.py

6.2 apps.py

一般这个就是定义这个应用的名称

arduino 复制代码

from django.apps import AppConfig
class CarConfig(AppConfig):
    default_auto_field = 'django.db.models.BigAutoField'
    name = 'car'

6.3 models.py

这个文件一般定义这个应用里面所涉及到的表以及字段

ini 复制代码

from django.db import models

class vehicle_info(models.Model):
    # 定义字段
    vehicle_name = models.CharField(max_length=255, verbose_name='车辆名称')
    year = models.IntegerField(verbose_name='生产年份')
    price = models.DecimalField(max_digits=10, decimal_places=2, verbose_name='车辆价格')
    description = models.CharField(max_length=255, blank=True, null=True, verbose_name='介绍 & 备注')

    def __str__(self):
        return self.vehicle_name

    class Meta:
        verbose_name = '车辆信息'
        verbose_name_plural = '车辆信息'



class vehicle_type_tab(models.Model):
    # 定义字段
    vehicle_id = models.IntegerField(verbose_name='车辆 ID')
    type_name = models.CharField(max_length=255, verbose_name='车辆类型名称')

    def __str__(self):
        return self.type_name

    class Meta:
        verbose_name = '车辆类型'
        verbose_name_plural = '车辆类型'



class vehicle_accessory_tab(models.Model):
    vehicle = models.ForeignKey(vehicle_info, on_delete=models.CASCADE, related_name='accessories', verbose_name='车辆')
    accessory_name = models.CharField(max_length=255, verbose_name='配件名称')
    price = models.DecimalField(max_digits=10, decimal_places=2, verbose_name='配件价格')

    def __str__(self):
        return self.accessory_name

    class Meta:
        verbose_name = '车辆配件'
        verbose_name_plural = '车辆配件'

6.4 urls.py

该文件用于定义这个应用里面所涉及到的接口里面是DRF的写法

lua 复制代码

from django.urls import path
from .views import AddVehicleView, VehicleListView, UpdateVehiclePricesView, DeleteVehiclesView

urlpatterns = [
    path('vehicles/add/', AddVehicleView.as_view(), name='add-vehicle'),
    path('vehicles/', VehicleListView.as_view(), name='vehicle-list'),
    path('vehicles/update-prices/', UpdateVehiclePricesView.as_view(), name='update-vehicle-prices'),
    path('vehicles/delete-old/', DeleteVehiclesView.as_view(), name='delete-vehicles'),
]

6.5 views.py

该文件写核心的逻辑代码

ini 复制代码

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework import generics, filters, status
from rest_framework.parsers import JSONParser
from django.db import transaction
from django.db.models import F
from django.db.models import Count, Sum, FloatField
from django.db.models.functions import Coalesce
from django.db.models import OuterRef, Subquery
from car.models import vehicle_info, vehicle_type_tab, vehicle_accessory_tab
from .serializers import VehicleInfoSerializer
from .pagination import VehiclePagination


# 添加数据
class AddVehicleView(APIView):
    parser_classes = [JSONParser]
    def post(self, request):
        data = request.data
        try:
            with transaction.atomic():
                vehicle = vehicle_info.objects.create(
                    vehicle_name=data['vehicle_name'],
                    year=data['year'],
                    price=data['price'],
                    description=data.get('description', '')
                )
                vehicle_type_tab.objects.create(
                    vehicle_id=vehicle.id,
                    type_name=data['type_name']
                )
                for accessory in data.get('accessories', []):
                    vehicle_accessory_tab.objects.create(
                        vehicle_id=vehicle.id,
                        accessory_name=accessory['name'],
                        price=accessory['price']
                    )
            return Response({'status': 'success'}, status=status.HTTP_201_CREATED)
        except Exception as e:
            return Response({'status': 'error', 'message': str(e)}, status=status.HTTP_400_BAD_REQUEST)

# 分页筛选数据
class VehicleListView(generics.ListAPIView):
    queryset = vehicle_info.objects.all()
    serializer_class = VehicleInfoSerializer
    pagination_class = VehiclePagination

    def get(self, request, *args, **kwargs):
        queryset = vehicle_info.objects.all()
        params = self.request.query_params

        keyword = params.get('keyword')
        if keyword:
            queryset = queryset.filter(vehicle_name__icontains=keyword)

        min_year = params.get('minYear')
        if min_year:
            queryset = queryset.filter(year__gte=min_year)

        max_year = params.get('maxYear')
        if max_year:
            queryset = queryset.filter(year__lte=max_year)

        min_price = params.get('minPrice')
        if min_price:
            queryset = queryset.filter(price__gte=min_price)

        # 注入车辆类型
        type_subquery = vehicle_type_tab.objects.filter(vehicle_id=OuterRef('pk')).values('type_name')[:1]

        queryset = queryset.annotate(
            type=Subquery(type_subquery),
            accessoryCount=Count('accessories'),
            totalAccessoryPrice=Coalesce(Sum('accessories__price', output_field=FloatField()), 0.0)
        )

        return Response({'data': list(queryset.values())}, status=status.HTTP_200_OK)

# 更新指定的字段
class UpdateVehiclePricesView(APIView):
    def post(self, request):
        try:
            with transaction.atomic():
                target_name = request.data.get('vehicle_name', 'CarB')
                target_price = float(request.data.get('target_price', 130000.0))
                increase_amount = float(request.data.get('increase_amount', 5000.0))
                block_year = int(request.data.get('block_year', 2019))
                initial_prices = list(vehicle_info.objects.all().values('id', 'price'))
                initial_accessory_prices = list(vehicle_accessory_tab.objects.all().values('id', 'price'))
                vehicle_info.objects.filter(vehicle_name=target_name).update(price=target_price)
                vehicle_info.objects.exclude(vehicle_name=target_name).update(price=F('price') + increase_amount)
                vehicles_to_check = vehicle_info.objects.filter(year__lt=block_year, price__gte=target_price)
                if vehicles_to_check.exists():
                    raise ValueError(f"存在年份早于 {block_year} 且价格高于 {target_price} 的车辆，禁止操作。")
                return Response({'status': 'success'}, status=status.HTTP_200_OK)
        except Exception as e:
            return Response({'status': 'error', 'message': str(e)}, status=status.HTTP_400_BAD_REQUEST)

# 条件删除
class DeleteVehiclesView(APIView):
    def post(self, request):
        try:
            with transaction.atomic():
                delete_before_year = int(request.data.get('year', 2019))
                vehicles_to_delete = vehicle_info.objects.filter(year__lt=delete_before_year)
                vehicle_ids = list(vehicles_to_delete.values_list('id', flat=True))
                deleted_vehicles_count = vehicles_to_delete.count()
                deleted_types_count = vehicle_type_tab.objects.filter(vehicle_id__in=vehicle_ids).count()
                deleted_accessories_count = vehicle_accessory_tab.objects.filter(vehicle_id__in=vehicle_ids).count()
                vehicle_type_tab.objects.filter(vehicle_id__in=vehicle_ids).delete()
                vehicle_accessory_tab.objects.filter(vehicle_id__in=vehicle_ids).delete()
                vehicles_to_delete.delete()
                return Response({
                    "deletedVehicles": deleted_vehicles_count,
                    "deletedTypes": deleted_types_count,
                    "deletedAccessories": deleted_accessories_count
                }, status=status.HTTP_200_OK)
        except Exception as e:
            return Response({'status': 'error', 'message': str(e)}, status=status.HTTP_400_BAD_REQUEST)