Python学习第150天（目前正在做的内容介绍）

目前正在按照相关教程制作一个具有班级、学生、老师三者之间相互关系的网页操作。目前暂时完成学生和班级部分内容，最为关键的manytomany班级与老师之间的关系还没有完善，这个小例子对实际操作的过程使用非常有帮助，以下是近期代码内容：

model.py

from django.db import models

class Classes(models.Model):
    # 班级表
    titile = models.CharField(max_length=32)
    m = models.ManyToManyField('Teachers')

class Teachers(models.Model):
    # 老师表
    name = models.CharField(max_length=36)

class Students(models.Model):
    username = models.CharField(max_length=32)
    age = models.IntegerField()
    gender = models.BooleanField()
    cs = models.ForeignKey(Classes, on_delete=None)

url.py

from django.contrib import admin
from django.urls import path,re_path
from app01.views import classes
from app01.views import students

urlpatterns = [
    path('admin/', admin.site.urls),
    re_path('^classes.html$',classes.get_classes),
    re_path('^add_classes.html$',classes.add_classes),
    re_path('^del_classes.html$',classes.del_classes),
    re_path('^edit_classes.html$',classes.edit_classes),

    re_path('^students.html$',students.get_students),
    re_path('^add_students.html$',students.add_studens),
    re_path('^del_students.html$',students.del_students),
    re_path('^edit_students.html$',students.edit_students)

    # re_path('^set_teacher.html$',classes.set_teacher),
    # path('a',classes.a_test),
    # path('b',classes.b_test),
]

classes.py

from django.shortcuts import render
from django.shortcuts import redirect
from app01 import models

def get_classes(req):
    cls_list = models.Classes.objects.all()
    for item in cls_list:
        print(item.id,item.titile,item.m.all())
    return render(req,'get_classes.html',{'cls_list':cls_list})

def add_classes(req):
    if req.method == 'GET':
        return render(req,'add_classes.html')
    elif req.method == 'POST':
        title = req.POST.get('title')
        models.Classes.objects.create(titile = title)
        return redirect('/classes.html')

def del_classes(req):
    nid = req.GET.get('nid')
    print(nid)
    models.Classes.objects.filter(id=nid).delete()
    return redirect('/classes.html')

def edit_classes(req):
    if req.method == 'GET':
        nid = req.GET.get('nid')
        obj = models.Classes.objects.filter(id=nid).first()
        return render(req,'edit_classes.html',{'obj':obj})
    elif req.method == 'POST':
        nid = req.GET.get('nid')
        title = req.POST.get('xoxo')
        models.Classes.objects.filter(id=nid).update(titile = title)
        return redirect('/classes.html')

students.py

from django.shortcuts import render,redirect
from app01 import models

def get_students(req):
    stu_list = models.Students.objects.all()
    return render(req,'get_students.html',{'stu_list':stu_list})

def add_studens(req):
    if req.method == 'GET':
        cs_list = models.Classes.objects.all()
        return render(req,'add_students.html',{'cs_list':cs_list})
    elif req.method == 'POST':
        u = req.POST.get('username')
        a = req.POST.get('age')
        g = req.POST.get('gender')
        c = req.POST.get('cs')
        print(u,a,g,c)
        models.Students.objects.create(
            username=u,
            age=a,
            gender=g,
            cs_id=c
        )
        return redirect('/students.html')

def del_students(req):
    nid = req.GET.get('nid')
    models.Students.objects.filter(id=nid).delete()
    return redirect('/students.html')

def edit_students(req):
    if req.method == 'GET':
        nid = req.GET.get('nid')
        obj = models.Students.objects.filter(id=nid).first()
        cs_list = models.Classes.objects.all()
        return render(req, 'edit_students.html', {'obj': obj,'cs_list':cs_list})
    elif req.method == 'POST':
        nid = req.GET.get('nid')
        cs_list = models.Classes.objects.all()
        # title = req.POST.get('xoxo')
        u = req.POST.get('username')
        a = req.POST.get('age')
        g = req.POST.get('gender')
        c = req.POST.get('c')
        models.Students.objects.filter(id=nid).update(
            username=u,
            age=a,
            gender=g,
            cs_id=c
        )
        return redirect('/students.html')

其中最为关键的一个视图模板

edit_students.html的内容

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <form action="edit_students.html?nid={{ obj.id }}" method="POST">
        {% csrf_token %}
{#        <p style="display: none"> <input type="text" name="id" value="{{ obj.id }}" /></p>#}
        <p> <input type="text" name="username" value="{{ obj.username }}" /></p>
        <p> <input type="text" name="age" value="{{ obj.age }}" /></p>
        <p>
            {% if obj.gender %}
                男：<input type="radio" name="gender" checked="checked" value="1" />
                女：<input type="radio" name="gender" value="0" />
                {% else %}
                男：<input type="radio" name="gender" value="1" />
                女：<input type="radio" name="gender" value="0" checked="checked"  />
            {% endif %}
        </p>
        <p>
            <select name="c">
                {% for row in cs_list %}
                    <option value="{{ row.id }}">{{ row.titile }}</option>
                {% endfor %}
            </select>
        </p>
        <input type="submit" value="提交" />
    </form>

</body>
</html>

目前已经完成了基本功能，完整功能还是等这个部分全部做完后进行详述。

关键的几个注意点：

1. 类代表数据库表
2. 类的对象代指数据库的一行记录
3.ForeignKey字段代指关联表中的一行数据（类的对象）

4.
- 正向：fk字段 (*****)
- 反向：小写类名_set(默认) ==> related_name='ssss'

5. 谁是主表？就全部列出其数据
models.Student.objects.all().values('username', 'cs__titile')
models.Classes.objects.all().values('titile', 'ssss__username')

4. M2M字段，自动生成第三张表；依赖关联表对第三张表间接操作

5.filter在查找的过程中涉及外键，可使用双下划线不断向下查询

以上为目前暂时更新的内容。