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Django?模型（数据库）

时间：2021-07-01 10:21:17 帮助过：18人阅读

Django 模型是与数据库相关的，与数据库相关的代码一般写在 models.py 中，Django 支持 sqlite3, MySQL, PostgreSQL等数据库，只需要在settings.py中配置即可，不用更改models.py中的代码。

大家可以按照我的步骤来开始做：

123	`django-admin.py startproject learn_models` `# 新建一个项目cd` `learn_models` `#进入到该项目的文件夹django-admin.py startapp blog_app` `#新建一个` blog_app 应用（app)

1、新建的应用（blog_app）添加到 settings.py 中的 INSTALLED_APPS中，也就是告诉Django有这么一个应用。 vim setting.py

<code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">    INSTALLED_APPS </span><span class="pun" style="color: rgb(147, 161, 161);">=</span><span class="pln" style="color: rgb(72, 72, 76);"> </span><span class="pun" style="color: rgb(147, 161, 161);">[</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">    </span><span class="str" style="color: rgb(221, 17, 68);">‘django.contrib.admin‘</span><span class="pun" style="color: rgb(147, 161, 161);">,</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">    </span><span class="str" style="color: rgb(221, 17, 68);">‘django.contrib.auth‘</span><span class="pun" style="color: rgb(147, 161, 161);">,</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">    </span><span class="str" style="color: rgb(221, 17, 68);">‘django.contrib.contenttypes‘</span><span class="pun" style="color: rgb(147, 161, 161);">,</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">    </span><span class="str" style="color: rgb(221, 17, 68);">‘django.contrib.sessions‘</span><span class="pun" style="color: rgb(147, 161, 161);">,</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">    </span><span class="str" style="color: rgb(221, 17, 68);">‘django.contrib.messages‘</span><span class="pun" style="color: rgb(147, 161, 161);">,</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">    </span><span class="str" style="color: rgb(221, 17, 68);">‘django.contrib.staticfiles‘</span><span class="pun" style="color: rgb(147, 161, 161);">,</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">    </span><span class="str" style="color: rgb(221, 17, 68);">‘blog_app‘</span><span class="pun" style="color: rgb(147, 161, 161);">,</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">    </span><span class="str" style="color: rgb(221, 17, 68);">‘web_app‘</span><span class="pun" style="color: rgb(147, 161, 161);">,</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">    </span><span class="pun" style="color: rgb(147, 161, 161);">]</span></font></code>

2、blog_app/models.py 文件，修改其中的代码, vim blog_app/model.py

<code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">
from django</span><span class="pun" style="color: rgb(147, 161, 161);">.</span><span class="pln" style="color: rgb(72, 72, 76);">db </span><span class="kwd" style="color: rgb(30, 52, 123);">import</span><span class="pln" style="color: rgb(72, 72, 76);"> models</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><span class="pln" style="color: rgb(72, 72, 76);"><font face="微软雅黑">
</font></span></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">
</span><span class="kwd" style="color: rgb(30, 52, 123);">class</span><span class="pln" style="color: rgb(72, 72, 76);"> </span><span class="typ" style="color: teal;">UserInfo</span><span class="pun" style="color: rgb(147, 161, 161);">(</span><span class="pln" style="color: rgb(72, 72, 76);">models</span><span class="pun" style="color: rgb(147, 161, 161);">.</span><span class="typ" style="color: teal;">Model</span><span class="pun" style="color: rgb(147, 161, 161);">):</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">        username </span><span class="pun" style="color: rgb(147, 161, 161);">=</span><span class="pln" style="color: rgb(72, 72, 76);"> models</span><span class="pun" style="color: rgb(147, 161, 161);">.</span><span class="typ" style="color: teal;">CharField</span><span class="pun" style="color: rgb(147, 161, 161);">(</span><span class="pln" style="color: rgb(72, 72, 76);">max_length</span><span class="pun" style="color: rgb(147, 161, 161);">=</span><span class="lit" style="color: rgb(25, 95, 145);">50</span><span class="pun" style="color: rgb(147, 161, 161);">)</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">        email </span><span class="pun" style="color: rgb(147, 161, 161);">=</span><span class="pln" style="color: rgb(72, 72, 76);"> models</span><span class="pun" style="color: rgb(147, 161, 161);">.</span><span class="typ" style="color: teal;">EmailField</span><span class="pun" style="color: rgb(147, 161, 161);">()</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">        memo </span><span class="pun" style="color: rgb(147, 161, 161);">=</span><span class="pln" style="color: rgb(72, 72, 76);"> models</span><span class="pun" style="color: rgb(147, 161, 161);">.</span><span class="typ" style="color: teal;">TextField</span><span class="pun" style="color: rgb(147, 161, 161);">()</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><span class="pun" style="color: rgb(147, 161, 161);"><font face="微软雅黑">   </font></span></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><span class="pun" style="color: rgb(147, 161, 161);"><font face="微软雅黑">    <font color="#000000">def __unicode__(self):
        </font><font color="#ff0000"># 在Python3中使用 def __str__(self)</font><font color="#000000">
        return self.username    </font></font></span></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><span class="pun" style="color: rgb(147, 161, 161);"><font face="微软雅黑">    </font></span></code>

PS: 我们新建了一个UserInfo类，继承自models.Model, 一个人有姓名和年龄。这里用到了三种Field。
3、我们来同步一下数据库注意：Django 1.7 及以上的版本需要用以下命令

<code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">python manage</span><span class="pun" style="color: rgb(147, 161, 161);">.</span><span class="pln" style="color: rgb(72, 72, 76);">py makemigrations</span></font></code><code class="language-c" style="font-family: Consolas, ‘Liberation Mono‘, Menlo, Courier, monospace; word-wrap: break-word;"><font face="微软雅黑"><span class="pln" style="color: rgb(72, 72, 76);">python manage</span><span class="pun" style="color: rgb(147, 161, 161);">.</span><span class="pln" style="color: rgb(72, 72, 76);">py migrate</span></font></code>

然后,我们会看到，Django生成了一系列的表，也生成了我们新建的UserInfo 这个表，那么如何使用这个表呢？ Django提供了丰富的API, 下面演示如何使用它。
>>>>>>

Django提供了丰富的API, 下面演示如何使用它。

123456 $ python manage.py shell >>> from people.models import UserInfo>>> UserInfo.objects.create(name="zhangsan", age=24)<Person: Person object>>>>

我们新建了一个用户zhangsan 那么如何从数据库是查询到它呢？

123	`>>> Userinfo.objects.get(name="zhangsan")<`UserInfo`:` UserInfo `object>>>>`

我们用了一个 .objects.get() 方法查询出来符合条件的对象，但是大家注意到了没有，查询结果中显示<UserInfo:UserInfo object>，这里并没有显示出与zhangsan的相关信息，如果用户多了就无法知道查询出来的到底是谁，查询结果是否正确，我们重新修改一下 blog_app/models.py

1、name 和 age 等字段中不能有 __（双下划线，因为在Django QuerySet API中有特殊含义（用于关系，包含，不区分大小写，以什么开头或结尾，日期的大于小于，正则等）

2、也不能有Python中的关键字，name 是合法的，student_name 也合法，但是student__name不合法，try, class, continue 也不合法，因为它是Python的关键字( import keyword; print(keyword.kwlist) 可以打出所有的关键字)

来源： http://www.ziqiangxuetang.com/django/django-models.html

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Django?模型（数据库）

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Django?模型（数据库）

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