Django Web开发入门基础

news2025/5/24 10:48:28

官方有很详细的文档，但是看过几遍之后如果要翻找还是有点麻烦，本文算作是学习笔记，提取一些关键点记录下来，另附上官方教程 Writing your first Django app

注：文中的指令使用py，是在Windows上，macOS要使用 python3

1. 安装Django

Django 是一个基于 Python 的Web开发框架，安装前可以用下面的命令检查是否安装了 Django，如果已经安装，会显示版本，没有安装会提示没有该模块

py -m django --version

如果没有安装，可以使用下面的命令安装

py -m pip install Django

2. 创建项目

项目就是一个 project，一个项目可以包含多个 app，也可以理解为多个模块，创建项目使用如下命令，其中 mysite 是项目名称：

django-admin startproject mysite

在令窗口中，切到刚刚创建的项目的根目录（有 manage.py），在项目中创建一个app，名字就叫 polls

py manage.py startapp polls

然后修改几个文件

polls/views.py

from django.http import HttpResponse

def index(request):
    return HttpResponse("Hello World!")

polls/urls.py

from django.urls import path
from . import views

urlpatterns = [
    path("", views.index, name="index"),
]

mysite/urls.py

from django.contrib import admin
from django.urls import include, path

urlpatterns = [
    path("polls/", include("polls.urls")),
    path("admin/", admin.site.urls),
]

最后启动服务，浏览器访问 http://localhost:8000/polls/

py manage.py runserver

3. 配置语言和时区

项目配置在 mysite/settings.py

语言标识可以在这里查找 Language Identifiers (RFC 3066)

# 语言设置为中文
LANGUAGE_CODE = 'zh-Hans'

时区标识可以在这里查找 List of tz database time zones

# 时区设置为北京时间
TIME_ZONE = 'Asia/Shanghai'

4. 数据库

就使用自带的 SQLite 吧，方便又简单，如果开发商用的Web App，建议使用其他数据库，要进行额外的配置。

（1）创建数据模型

修改 polls/models.py

import datetime

from django.db import models
from django.utils import timezone

class Question(models.Model):
	question_text = models.CharField(max_length=200)
	pub_date = models.DateTimeField("date published")

	def __str__(self):
		return self.question_text

	def was_published_recently(self):
		return self.pub_date >= timezone.now() - datetime.timedelta(days=1)


class Choice(models.Model):
	# Choice属于一个Question
	question = models.ForeignKey(Question, on_delete=models.CASCADE)
	choice_text = models.CharField(max_length=200)
	votes = models.IntegerField(default=0)

	def __str__(self):
		return self.choice_text

（2）激活模型

修改 mysite/settings.py，在 INSTALLED_APP 中添加 polls.apps.PollsConfig

INSTALLED_APPS = [
    "polls.apps.PollsConfig",
    "django.contrib.admin",
    "django.contrib.auth",
    "django.contrib.contenttypes",
    "django.contrib.sessions",
    "django.contrib.messages",
    "django.contrib.staticfiles",
]

（3）创建数据迁移(尚未提交)

py manage.py makemigrations polls

查看创建的迁移使用的SQL语句，下面命令中的 0001 是上面创建迁移时生成的 polls/migrations/0001_initial.py 文件名中的数字

py manage.py sqlmigrate polls 0001

（4）提交迁移

py manage.py migrate

总结起来就三步：修改模型 -> 创建迁移 -> 提交迁移

（5）玩转数据库API

打开交互式窗口

py manage.py shell

>>> from polls.models import Choice, Question
>>> Question.objects.all()
<QuerySet []>
>>> from django.utils import timezone
>>> q = Question(question_text="What's new?", pub_date=timezone.now())
>>> q.save()
>>> q.id
1
>>> q.question_text
"What's new?"
>>> q.pub_date
datetime.datetime(2012, 2, 26, 13, 0, 0, 775217, tzinfo=datetime.timezone.utc)
>>> q.question_text = "What's up?"
>>> q.save()
>>> Question.objects.all()
<QuerySet [<Question: Question object (1)>]>

>>> from polls.models import Choice, Question
>>> Question.objects.all()
<QuerySet [<Question: What's up?>]>
>>> Question.objects.filter(id=1)
<QuerySet [<Question: What's up?>]>
>>> Question.objects.filter(question_text__startswith="What")
<QuerySet [<Question: What's up?>]>
>>> from django.utils import timezone
>>> current_year = timezone.now().year
>>> Question.objects.get(pub_date__year=current_year)
<Question: What's up?>
>>> Question.objects.get(id=2)
Traceback (most recent call last):
    ...
DoesNotExist: Question matching query does not exist.
>>> Question.objects.get(pk=1)
<Question: What's up?>
>>> q = Question.objects.get(pk=1)
>>> q.was_published_recently()
True
>>> q = Question.objects.get(pk=1)
>>> q.choice_set.all()
<QuerySet []>
>>> q.choice_set.create(choice_text="Not much", votes=0)
<Choice: Not much>
>>> q.choice_set.create(choice_text="The sky", votes=0)
<Choice: The sky>
>>> c = q.choice_set.create(choice_text="Just hacking again", votes=0)
>>> c.question
<Question: What's up?>

>>> q.choice_set.all()
<QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]>
>>> q.choice_set.count()
3
>>> Choice.objects.filter(question__pub_date__year=current_year)
<QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]>
>>> c = q.choice_set.filter(choice_text__startswith="Just hacking")
>>> c.delete()