本文主要演示
- django 连接 mysql
- python 模型同步到数据库
- CRUD api
- django 后台管理页面
连接 mysql
通过 pymysql 连接
（mysqlclient 依赖弄了半天没弄好，使用 pymysql就连接上了）
pip install --upgrade pymysql
pip show pymysql
DB 配置
mysite/settings.py
DATABASES = {
'default': {
"ENGINE": "django.db.backends.mysql",
"USER": "root",
"PASSWORD": "root",
"HOST": "localhost",
"PORT": "3306",
}
}
创建模型
每个模型被表示为 django.db.models.Model 类的子类
polls/models.py
from django.db import models
class Question(models.Model):
question_text = models.CharField(max_length=200)
pub_date = models.DateTimeField("date published")
class Choice(models.Model):
question = models.ForeignKey(Question, on_delete=models.CASCADE)
choice_text = models.CharField(max_length=200)
votes = models.IntegerField(default=0)
激活模型
mysite/settings.py添加polls.app.PollsConfig路径
生成迁移文件
python manage.py makemigrations polls
预览迁移 SQL
$ python manage.py sqlmigrate polls 0001
--
-- Create model Question
--
CREATE TABLE `polls_question` (`id` bigint AUTO_INCREMENT NOT NULL PRIMARY KEY, `question_text` varchar(200) NOT NULL, `pub_date` datetime(6) NOT NULL);
--
-- Create model Choice
--
CREATE TABLE `polls_choice` (`id` bigint AUTO_INCREMENT NOT NULL PRIMARY KEY, `choice_text` varchar(200) NOT NULL, `votes` integer NOT NULL, `question_id` bigint NOT NULL);
ALTER TABLE `polls_choice` ADD CONSTRAINT `polls_choice_question_id_c5b4b260_fk_polls_question_id` FOREIGN KEY (`question_id`) REFERENCES `polls_question` (`id`);
(py3.12)
检查项目问题
$ python manage.py check
System check identified no issues (0 silenced).
(py3.12)
执行迁移
- 功能类似于Mybatis自动generate数据库
- Django 通过在数据库中创建一个特殊的表
django_migrations来跟踪执行过哪些迁移）并应用在数据库上 - 也就是将你对模型的更改同步到数据库结构上
$ python manage.py migrate
Operations to perform:
Apply all migrations: admin, auth, contenttypes, polls, sessions
Running migrations:
Applying contenttypes.0001_initial... OK
Applying auth.0001_initial... OK
Applying admin.0001_initial... OK
Applying admin.0002_logentry_remove_auto_add... OK
Applying admin.0003_logentry_add_action_flag_choices... OK
Applying contenttypes.0002_remove_content_type_name... OK
Applying auth.0002_alter_permission_name_max_length... OK
Applying auth.0003_alter_user_email_max_length... OK
Applying auth.0004_alter_user_username_opts... OK
Applying auth.0005_alter_user_last_login_null... OK
Applying auth.0006_require_contenttypes_0002... OK
Applying auth.0007_alter_validators_add_error_messages... OK
Applying auth.0008_alter_user_username_max_length... OK
Applying auth.0009_alter_user_last_name_max_length... OK
Applying auth.0010_alter_group_name_max_length... OK
Applying auth.0011_update_proxy_permissions... OK
Applying auth.0012_alter_user_first_name_max_length... OK
Applying polls.0001_initial... OK
Applying sessions.0001_initial... OK
(py3.12)
检查数据库，可以看到生成了数据表
小结
- 编辑
models.py文件，改变模型。 - 运行
python manage.py makemigrations为模型的改变生成迁移文件。 - 运行
python manage.py migrate来应用数据库迁移。
交互式 api
体验 CRUD api
$ python 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(2024, 9, 15, 3, 13, 45, 532040, tzinfo=datetime.timezone.utc)
>>> q.question_text = "What's up?"
>>> q.save()
>>> Question.objects.all()
<QuerySet [<Question: Question object (1)>]>
>>> quit()
(py3.12)
添加代码后再进入 shell
$ python manage.py shell
>>> 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):
File "<console>", line 1, in <module>
File "/Users/wateryes/Desktop/pyvenv/py3.12/lib/python3.12/site-packages/django/db/models/manager.py", line 87, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/wateryes/Desktop/pyvenv/py3.12/lib/python3.12/site-packages/django/db/models/query.py", line 649, in get
raise self.model.DoesNotExist(
polls.models.Question.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()
(1, {'polls.Choice': 1})
>>>
Django 管理页面
创建管理员
- 账密 admin | admin
$ python manage.py createsuperuser
Username (leave blank to use 'wateryes'): admin
Email address: admin@example.com
Password:
Password (again):
The password is too similar to the username.
This password is too short. It must contain at least 8 characters.
This password is too common.
Bypass password validation and create user anyway? [y/N]: y
Superuser created successfully.
(py3.12)
启动开发服务器
python manage.py runserver
http://127.0.0.1:8000/admin/login/?next=/admin/
登录
管理后台管理页
向管理页面中加入投票应用 polls
打开 polls/admin.py 文件，把它编辑成下面这样
from django.contrib import admin
from .models import Question
admin.site.register(Question)
此时，查看管理页面可以看到已经添加 polls
