Python从入门到实践project Web 应⽤程序Django入门.1

python -m venv ll_env

.ll_envScriptsactivate

# 更新pip
 python.exe -m pip install --upgrade pip

# 安装Django
pip install django

django-admin startproject ll_project
  ls

ls ll_project

python manage.py migrate

ls

#打开激活的虚拟环境并查看相关文件
 .ll_envScriptsactivate
 python manage.py startapp learning_logs    # 搭建创建应⽤程序所需的基础设施。
 ls

ls learning_logs/

class Topic(models.Model):      # 创建⼀个名为 Topic 的类，并继承 Model
    """⽤户学习的主题"""
    text = models.CharField(max_length=200)   # models.CharField设置存储文本属性，max_length=200大小为200字符
    date_added = models.DateTimeField(auto_now_add=True)
    # models.DateTimeField记录⽇期和时间的数据 auto_now_add=True 自动传入当前日期

    def __str__(self):
        """返回模型的字符串表⽰"""
        return self.text
        # 返回属性 text 的值

# 我的应⽤程序
 'learning_logs',
 # Django 默认添加的应⽤程序

python manage.py makemigrations learning_logs

python manage.py migrate

python manage.py createsuperuser

from .models import Topic    # 导⼊要注册的模型 Topic
admin.site.register(Topic)   # admin.site.register()让 Django 通过管理网站管理模型

class Entry(models.Model):
    """学到的有关某个主题的具体知识"""
    topic = models.ForeignKey(Topic, on_delete=models.CASCADE)
    # models.ForeignKey（外键）关联主题 models.CASCADE（级联删除）在删除主题的同时删除所有与之相关联的条⽬
    text = models.TextField()   # 实例
    date_added = models.DateTimeField(auto_now_add=True)  # 创建顺序呈现条⽬，并在每个条⽬旁边放置时间戳

    class Meta:
        """Meta 存储⽤于管理模型的额外信息"""
        verbose_name_plural = 'entries'  # 使⽤ Entries 表⽰多个条⽬

    def __str__(self):
        """返回⼀个表⽰条⽬的简单字符串"""
        return f"{self.text[:50]}..."
        # 只返回 text 的前 50 个字符

.ll_envScriptsactivate

python manage.py makemigrations learning_logs

python manage.py migrate

from .models import Topic, Entry
admin.site.register(Entry)

返回 http://localhost/admin/，将看到 Learning_Logs 下列出了 Entries
单击 Entries 再选择 Add entry

从下拉列表中选择 Chess，并添加⼀个条⽬

The opening is the first part of the game, roughly the first ten moves or so. In
the opening, it's a good idea to do three things— bring out your bishops and
knights, try to control the center of the board, and castle your king.（国际象
棋的第⼀个阶段是开局，⼤概是前 10 步左右。在开局阶段，最好做三
件事情：将象和⻢调出来，努⼒控制棋盘的中间区域，以及⽤⻋将王
护住。）
Of course, these are just guidelines. It will be important to learn when to
follow these guidelines and when to disregard these suggestions.（当然，这
些只是指导原则。学习在什么情况下遵守、在什么情况下不⽤遵守这
些原则很重要。）

In the opening phase of the game, it's important to bring out your bishops
and knights. These pieces are powerful and maneuverable enough to play a
significant role in the beginning moves of a game.（在国际象棋的开局阶
段，将象和⻢调出来很重要。这些棋⼦威⼒⼤、机动性强，在开局阶
段扮演着重要的⾓⾊。）

One of the most important concepts in climbing is to keep your weight on
your feet as much as possible. There's a myth that climbers can hang all day
on their arms. In reality, good climbers have practiced specific ways of
keeping their weight over their feet whenever possible.（最重要的攀岩概
念之⼀是，尽可能让双脚承受体重。有⼈误认为攀岩者能依靠⼿臂的
⼒量坚持攀岩⼀整天。实际上，优秀的攀岩者都经过专门训练，能够
尽可能让双脚承受体重。）

python manage.py shell

from learning_logs.models import Topic
Topic.objects.all()   # 获取模型 Topic 的所有实例

topics = Topic.objects.all()
 for topic in topics:
 	print(topic.id, topic)

t = Topic.objects.get(id=1)
 t.text
 t.date_added

t.服务器托管网entry_set.all()