Django Filter Queryset （Django 过滤查询）26-慕源网

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Django Filter Queryset介绍

在Django中建立数据库连接时，总是需要单独从数据库中提取所需的列及其对应的行，基本上是使用django模型过滤器中设置的过滤器查询来实现的。当期望从数据库中检索值时，面向查询集的提取的过滤器查询集部分就会发挥作用。提及特定列的过滤器将帮助我们从检索到的查询集中单独过滤和提取那些相应的值。django 中的这个选项帮助我们实现对所需值的抽象级别过滤。

语法：

过滤查询集的语法如下，

model.objects.filter(condition)

创建Queryset

以免讨论如何创建queryset。

1.在应用程序中创建一个models.py文件：这里需要在moedels.py文件中提到一个数据库的示意图结构。

例子：（models.py）

from django.db import models
# Create your models here.
class sample(models.Model):
name =  models.CharField(max_length=20,unique=True)
card_no =    models.IntegerField()
def _str_(Self):
return self.name, self.id

我们可以注意到示意图结构是作为引用模型导入的类创建的。模型的所有预期字段都需要在此类中声明。还要确保数据库配置到位，以便在访问数据库时不会产生问题，

示例：（SETTINGS.py）

TEMPLATES = [
{
'BACKEND': 'django.template.backends.django.DjangoTemplates',
'DIRS': [Template_DIR,],
'APP_DIRS': True,
'OPTIONS': {
'context_processors': [
'django.template.context_processors.debug',
'django.template.context_processors.request',
'django.contrib.auth.context_processors.auth',
'django.contrib.messages.context_processors.messages',
],
},
},
] WSGI_APPLICATION = 'educba.wsgi.application'
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql',
'NAME': 'postgres',
'USER': 'postgres',
'PASSWORD' : 'anand',
'HOST': '127.0.0.1',
'PORT': '5432',
}
}

2.检查迁移：创建模型文件后，使用 make migrations 命令验证预期的迁移。

python manage.py makemigrations

3.应用迁移：接下来，使用 migrate 命令应用所有需要的迁移。

python manage.py migrate

4.在views.py 文件中创建需要的视图：必须生成所有需要的视图。

views.py

from django.shortcuts import render
from django.http import  HttpResponse
from Django_app1.forms import Valueform,fileform,emailform,requestcheckform
from django.core.exceptions import ViewDoesNotExist
from django.contrib.auth.models import User
from django.core.files.storage import FileSystemStorage
from django.contrib import messages
from django.core.mail import send_mail,EmailMessage
from Django_app1.models import sample
import requests
def requestmethods(request):
form = requestcheckform()
if request.method == 'POST':
# REQUEST OBJECT ATTRIBUTES
if request.POST['request_attribute'] == 'Request Header':
data_content = "data content of request method : " + str(request.headers)
messages.success(request,data_content)
elif request.POST['request_attribute'] == 'Request POST':
post_content = "post content of request method : " + str(request.POST)
messages.success(request,post_content)
elif request.POST['request_attribute'] == 'Request Files':
FILES_content = "FILES in request method : " + str(request.FILES)
messages.success(request,FILES_content)
elif request.POST['request_attribute'] == 'Request GET':
GET_content = "GET Content in request method : " + str(request.GET)
messages.success(request,GET_content)
elif request.POST['request_attribute'] == 'Request User':
Request_User = "User Details : " + str(request.user)
messages.success(request,Request_User)
elif request.POST['request_attribute'] == 'Request Body':
Request_body = "Request Body : " + str(request.body)
messages.success(request,Request_body)
elif request.POST['request_attribute'] == 'Request Content Type':
Request_Content_Type = "Request Content type : " + str(request.content_type)
messages.success(request,Request_Content_Type)
elif request.POST['request_attribute'] == 'Request Encoding':
Request_Encoding = "Request Encoding Used : " + str(request.encoding)
messages.success(request,Request_Encoding )
elif request.POST['request_attribute'] == 'Request Method':
Request_method = "Request Method posted : " + str(request.method)
messages.success(request,Request_method )
elif request.POST['request_attribute'] == 'Request Path':
Request_path = "Path of the request : " + str(request.path)
messages.success(request,Request_path )
elif request.POST['request_attribute'] == 'Request Cookies':
Request_Cookies = "Cookies associated to the Request : " + str(request.COOKIES)
messages.success(request,Request_Cookies )
elif request.POST['request_attribute'] == 'Request META':
Request_META = "HTTP headers info : " + str(request.META)
messages.success(request,Request_META )
# REQUEST METHODS
elif request.POST['request_attribute'] == 'Request port':
Request_port =  "Request port number: " + str(request.get_port())
messages.success(request,Request_port )
elif request.POST['request_attribute'] == 'Request host':
Request_host =  "Requested Host: " + str(request.get_host())
messages.success(request,Request_host)
elif request.POST['request_attribute'] == 'Request is_secure':
Request_secure =  "Security level of the request: " + str(request.is_secure())
messages.success(request,Request_secure)
return  render(request,'Request_methods_check.html',{"form":form})
def file_upload(request):
file = fileform()
print(" File Values in File Dictionary :", request.FILES)
if request.method == 'POST' and request.FILES['Uploaded_File']:
uploaded_file = request.FILES['Uploaded_File'] fs = FileSystemStorage()
filename = fs.save(uploaded_file.name, uploaded_file)
uploaded_File_Size = 'Size of Uploaded file : ' + str(uploaded_file.size)
content_type_of_uploaded_file = 'Content type of uploaded file : ' + str(uploaded_file.content_type)
uploaded_file_name = 'Name of Uploaded file : ' + str(uploaded_file.name)
uploaded_file_url = fs.url(filename)
print("uploaded file url",uploaded_file_url)
messages.success(request, '!!! File upload successful !!!')
messages.success(request,uploaded_File_Size)
messages.success(request,uploaded_file_name)
messages.success(request,content_type_of_uploaded_file)
return render(request, 'filehandeling.html', {"file":file})
return render(request, 'filehandeling.html',{"file":file})
def email_sending(request):
email = emailform()
if request.method == 'POST':
email_id =  request.POST['email'] email_subject =  request.POST['email_subject'] email_message =  request.POST['email_message'] mail = send_mail(email_subject,email_message,'testmysmtpconnection@gmail.com',[email_id],fail_silently = False)
response = HttpResponse(mail)
print("Content of the resposne: ",response.content)
print("Charecterset of the response: ",response.charset)
print("Status code of the response: ",response.status_code)
print("Reason phrase of the response: ",response.reason_phrase)
print("Reason close status: ",response.closed)
return response
return render(request, 'emailpage.html',{"email":email})
def db_hit(request):
all_objects =  sample.objects.all()
for i in all_objects:
print(i.card_no)
print(sample.objects.filter(card_no = 102))
return render(request, 'model.html')

6.生成所需的模板：必须创建提及网页的模板。

model.html：

<!DOCTYPE html>
<html lang="en" dir="ltr">
<head>
<meta charset="utf-8">
<title>Django App1</title>
{% load static %}
<link href="{% static 'admin/css/font.css' %}" rel="stylesheet">
<style>
body {
background-image: url("{% static 'admin/img/background.jpg' %}");
background-color: #acccbb;
}
</style>
</head>
<body>
<h1> <u> MODEL HANDELING </u> </h1>
</body>
</html>

email_page.html：

<!DOCTYPE html>
<html lang="en" dir="ltr">
<head>
<meta charset="utf-8">
<title>Django App1</title>
{% load static %}
<link href="{% static 'admin/css/font.css' %}" rel="stylesheet">
<style>
body {
background-image: url("{% static 'admin/img/background.jpg' %}");
background-color: #acccbb;
}
.myDiv {
border: 5px outset red;
background-color: lightblue;
text-align: center;
font-family: "Comic Sans MS", cursive, sans-serif;
font-size: 14px;
letter-spacing: 2px;
word-spacing: 1.8px;
text-align: left;
color: #02071C;
font-weight: 200;
text-decoration: none;
font-style: normal;
font-variant: normal;
text-transform: capitalize;
}
</style>
</head>
<body>
<h1> <u> DJANGO HANDELING EMAILS </u> </h1>
<div class="myDiv" style = "max-width:470px;">
<form method =  'POST' ">
{{ email.as_p }}
{% csrf_token %}
<input type="submit" class="btn btn-primary" value="submit" style="text-align:center">
</form>
</div>
</body>
</html>

7.在 urls.py 文件中标记视图：这是为视图创建 url 的过程。

从 django.conf.urls import url 导入库
在 urlpatterns 列表中声明一个 url 条目

url(url_path, view_to_be_tagged, name_for_this_view)

urls.py：

from django.contrib import admin
from django.conf.urls import url
from Django_app1 import views
urlpatterns = [
url(r'formpage/',views.formView,name='form'),
url(r'fileupload/',views.file_upload,name='file_upload'),
url(r'emailpage/',views.email_sending,name='email_sending'),
url(r'requests/',views.Httpmethods,name='Request_check'),
url(r'requestmethod/',views.requestmethods,name='request_method'),
url(r'model/',views.db_hit,name='db_hit'),
]

输出：