Django QuerySet对象，filter()方法

filter()方法用于实现数据过滤功能，相当于sql语句中的where子句。

filter(字段名__exact=10) 或 filter(字段名=10)	类似sql 中的 =10
filter(字段名__gt=10)	类似SQL中的 >10
filter(price__lt=29.99)	类似sql中的 <29.99
filter(字段名__gte=10, 字段名__lte=20)	类似sql中的 >=10 and <=10 使用filter()方法获取所有价格在10到20之间的书籍

    # books = Book.objects.filter(price__gte=10, price__lte=20)  # __gte是“greater than or equal to”（大于等于）的缩写，__lte是“less than or equal to”（小于等于）的缩写。
    # books = Book.objects.filter(price__gt=10)   # 在Django的ORM（对象关系映射）查询中，__gt是过滤条件的一个特殊语法，用于表示“大于”（greater than）。
    books = Book.objects.filter(price__lt=29.99)   # __lt 是“less than”（小于）的缩写。

1，添加模型

Test/app11/models.py

from django.db import models

class Post(models.Model):
    title = models.CharField(max_length=200)
    content = models.TextField()
    pub_date = models.DateTimeField('date published')




class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.CharField(max_length=100)
    publication_date = models.DateField()
    price = models.DecimalField(max_digits=5, decimal_places=2)

    def __str__(self):
        return self.title

2，添加视图函数

Test/app11/views.py

from django.shortcuts import render
from .models import Post

def index(request):
    posts = Post.objects.all()
    return render(request, '11/index.html', {'posts': posts})



# apps/books/views.py

from django.shortcuts import render
from .models import Book

def book_list_view(request):
    # 使用filter()方法获取所有价格在10到20之间的书籍
    books = Book.objects.filter(price__gte=10, price__lte=20)
    return render(request, '11/book_list.html', {'books': books})

3，添加路由地址

Test/app11/urls.py

from django.urls import path
from . import views

urlpatterns = [
    path('index/', views.index, name='index'),
    path('book_list_view/', views.book_list_view, name='book_list_view'),
]

4，执行迁移

python manage.py makemigrations app11

python manage.py migrate app11

5，创建示例数据

Test/create_books.py

import os
import django

# 设置Django环境，需要指定settings模块
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "Test.settings")
django.setup()

from app11.models import Book

def create_books():
    # 创建示例书籍
    book1 = Book(title="Python编程", author="小强", publication_date="2022-01-01", price=15.99)
    book2 = Book(title="Django Web开发", author="小龙", publication_date="2022-04-15", price=29.99)
    book3 = Book(title="算法导论", author="小龙", publication_date="2024-07-20", price=19.99)
    book4 = Book(title="java入门到弃坑", author="余胜军", publication_date="2019-02-20", price=39.99)
    book5 = Book(title="c入门到弃坑", author="小龙", publication_date="2012-07-20", price=9.99)
    book6 = Book(title="c++入门到弃坑", author="小6", publication_date="2024-02-20", price=13.99)
    book7 = Book(title="python多线程入门", author="小6", publication_date="2025-02-20", price=49.99)

    # 保存书籍到数据库
    book1.save()
    book2.save()
    book3.save()
    book4.save()
    book5.save()
    book6.save()
    book7.save()

    print("数据创建成功！")

if __name__ == "__main__":
    create_books()