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Django学堂在线笔记-1

article 2025/1/18 9:05:58

1. 基本命令-扫盲向

a 新建一个项目后添加一个app(name: myapp for instance)

python manage.py startapp myapp

b 启动服务

python manage.py runserver

2. 复杂模版及变量传递

views.py

from django.shortcuts import render

from tem_app.Person import Person


# Create your views here.
def tem_var(request, name):
    return render(request, "show_var.html", {"name": name})


def pass_dict(request):
    product1 = {
        "name": "Django",
        "teacher": "李老师"
    }
    return render(request, "show_info.html", {"product": product1})


def pass_obj(request):
    p = Person("李文鹏", 18)
    return render(request, "show_info.html", {"person": p})

def pass_list(request):
    fruits = ["apple", "banana"]
    return render(request, "show_info.html", {"fruits": fruits})

def pass_all(request):
    product1 = {
        "name": "Django",
        "teacher": "李老师"
    }
    p = Person("李文鹏", 18)
    fruits = ["apple", "banana"]
    # return render(request, "show_info.html", {"product": product1, "person": p, "fruits": fruits}) # method1 for logic explain
    """"
    locals = {
        "request": request   # 也传递了一个request对象，具体原因下次再说
        "fruits": fruits,
        "product": product1,
        "p": p
    }
    """
    return render(request, "show_info.html", locals()) # method2: use locals() object

tem_app/urls.py 

"""
URL configuration for hw2 project.

The `urlpatterns` list routes URLs to views. For more information please see:
    https://docs.djangoproject.com/en/4.2/topics/http/urls/
Examples:
Function views
    1. Add an import:  from my_app import views
    2. Add a URL to urlpatterns:  path('', views.home, name='home')
Class-based views
    1. Add an import:  from other_app.views import Home
    2. Add a URL to urlpatterns:  path('', Home.as_view(), name='home')
Including another URLconf
    1. Import the include() function: from django.urls import include, path
    2. Add a URL to urlpatterns:  path('blog/', include('blog.urls'))
"""

from django.urls import path

from tem_app.views import pass_dict, tem_var, pass_obj, pass_list, pass_all

urlpatterns = [
    # path("admin/", admin.site.urls),
    path("var/<name>/", tem_var),
    path("dict/", pass_dict), # 传递字典
    path("obj/", pass_obj),  # 传递对象
    path("list/", pass_list), # 传递列表
    path("all/", pass_all)
]

3. 模版标签

a 简单if标签

{% if 布尔值 %}

布尔值为True时，显示的内容

{% else %}

布尔值为False时，显示的内容

{% endif %}

b 多分支if标签

{% if score >= 90  %}

优秀

{% if score >= 80  %}

良好

{% if score >= 60  %}

一般

{% else  %}

不合格

{% endif %}

c for标签
{% for fruit in fruits %}
            <li> {{ fruit }}</li>
        {% endfor %}

tag_for.html

    <!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>for标签</title>
    </head>
    <body>
    <ul>
       {% for fruit in fruits %}
            <li> {{ forloop.counter }} {{ fruit }}</li>
           {%  empty %}
           <h3> 什么都没有 </h3>
        {% endfor %}
        <hr>
        {% for item in items %}
            {{ item }}
            {% if not forloop.last %}
            |
            {% endif %}
        {% endfor %}

        <h4> Reversed order of items: </h4>
        {% for item in items reversed %}
            {{ item }}
            {% if not forloop.last %}
            |
            {% endif %}
        {% endfor %}

        <hr>
    </ul>

    </body>
    </html>
d include标签

{% include '包含的模版地址' %}

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>include标签</title>
</head>
<body>
欢迎访问我栋网站<br>
网站内容<br>



<hr>
{% include 'footer.html' %}
</body>
</html>

footer.html

友情链接： <a href="http://www.baidu.com"> 百度 </a> <br>
<a href="http://www.360.com"> 360 </a> <br>
<a href="http://www.sogou.com"> 搜狗 </a> <br>
<a href="http://121.40.143.58"> 多米的空中小屋 </a> <br>
<a href="http://www.sohu.com"> 搜狐 </a> <br>
联系电话：18010000000
e 模版继承标签

子模板：{% entends  父模版位置 %}

父模版：

        {% block 块名称 %}

        {% endblock %}

模版过滤器 

{{ 模版变量 ｜ 过滤器 }}

自定义模版过滤器

from django import template

register = template.Library()


@register.filter(name="abc")
def upper_number(value: int):
    try:
        return ["〇", "壹", "贰", "叁", "肆", "伍", "陆", "柒", "捌", "玖", "拾"][value]
    except IndexError:
        return "Error Params"

4. Django基础模型

4.1 mysql相关-基础

a 增

添加数据的两种方式

1. 通过对象管理器添加

Students.objects.add(name="梓潼", gender="男", score=12)

2. 通过实例化对象添加

s = Students(name="多米", gender="男", score=33)
s.save()

测试

### add data
```python

class StudentsTestCase(TestCase):
    def setUp(selfself) -> None:
        self.start_time = time.time()

    # Add data
    def test_insert_data(self):
        # Method1: Object manager
        Students.objects.create(name="test", gender="Male", score=99.5)
        print(f"Time Cost: {time.time() - self.start_time}")

        # Method2: Objectify the object
        s = Students(name="test", gender="Male", score="44.1")
        s.save()

        print(f"Time Cost: {time.time() - self.start_time}")

    def tearDown(self) -> None:
        print("Test Done")

```
b 改删
s1 = Students(name="韩梅梅", gender="女", score=67)
s1.save()

# modify
s1.name = "Xiaoming"
s1.save()
s1.gender="男"
s1.save()

# delete
s1.delete()
# Notice: no need save

c 查

简单模糊查询

c1 通过主键查询一条记录
# 通过主键 primary key
s1 = Students.objects.get(pk=1)

# 通过ID
s1 = Students.objects.get(id=1)

 c2 多条记录按索引访问
s = Students.objects.all()
# Then we will get a Students object(1)

s[0].name

# 即使查不到数据，返回的对象仍然是QuerySet，只是空而已
 c3 过滤查询

几个模糊查找的方式：

__contains: s = Students.objects.filter(name__contains="李")

__startswith: s = Students.objects.filter(name__startwith="韩")

__endswith: 

__gte: greater than or equal to

__lte: less than or equal to

__year

__month

__day

# python manage.py
python manage.py shell

# after join mysql and the command line start with <<<
s = Students.objects.filter(name__contains="李")
s
c4 异常处理 

插播一条如果在添加join_date字段的时候报错的处理过程，这里卡了一会儿，最后解决方案是把数据库删除重置修复的，命令如下：

DROP DATABASE my_django;

exit

mysql -u root -p

create database my_django;

use my_django

然后在Django端重新操作就好了，这里可以一遍添加一边查询查看数据库的更新过程：

c5 排除查询和限制查询
# query those whose score is greater and equal than --
s = Students.objects.filter(score__gte=80)
for i in s:
    print(i.name)
    print(i.score)
   
s = Students.objects.exclude(score__gte=80)
s
# output are like: <QuerySet []>

s = Students.objects.all()
c6 排序查询

c7 原生查询 raw()

可以再Django中直接嵌入mysql原生语句的查询方式

all_1 = Students.objects.all()
all = Students.objects.raw("select * from students;")

a = Students.objects.raw("select id, name from students where name like 't%%';")
for i in a:
    print(i.name)


s = Students.objects.raw("select * from students where name=%s and gender=%s", ["韩梅梅", "女"])
for i in s:
    print(i.name, "--", i.gender)

# generate migration script
python manage.py makemigrations

c8 Q查询

用于比较复杂的组合关系查询，filter查询不太好用的时候使用，首先注意需要先import Q！

下面是查询q1成绩大于90， q2名字不是以韩开头的数据：注意名字以什么支付开始的判断是startswith

s_all = Students.objects.all()
[i.name for i in s_all]
# Query those score is > 80 and in start with "韩"

c9 F查询

同样要先导入F查询的包

c10 聚合查询

要对数据做一些聚合运算，统计下平均值，总数等

from django import Sum, Avg, Max, Min, Count

avg_score = Students.objects.all().aggregate(Avg("score"))
avg_score
avg_score = Students.objects.aggregate(Avg("score"))

c11 分组查询
score_avg = Students.objects.values("gender").annotate(Agv("score"))

4.2 综合演练

见笔记2


http://www.kler.cn/a/507625.html

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