MongoEngine - 排序

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QuerySet的order_by()函数用于以排序的方式获取查询结果。用法如下 -

Qset.order_by(‘fieldname’)

默认情况下，排序顺序为升序。对于降序排列，请在字段名称后附加 - 号。例如，要按升序获取价格明智的列表 -

from mongoengine import *
con=connect('newdb')

class products (Document):
   ProductID=IntField(required=True)
   company=StringField()
   Name=StringField()
   price=IntField()
for product in products.objects.order_by('price'):
   print ("Name:{} company:{} price:{}".format(product.Name, product.company, product.price))

输出

Name:Router company:Iball price:2000
Name:Scanner company:Cannon price:5000
Name:Printer company:Cannon price:12500
Name:Laptop company:Acer price:25000
Name:TV company:Philips price:31000
Name:Laptop company:Dell price:45000
Name:TV company:Samsung price:50000

以下代码将以名称降序获取列表 -

for product in products.objects.order_by('-Name'):
   print ("Name:{} company:{} price:{}".format(product.Name, product.company, product.price))

输出

Name:TV company:Samsung price:50000
Name:TV company:Philips price:31000
Name:Scanner company:Cannon price:5000
Name:Router company:Iball price:2000
Name:Printer company:Cannon price:12500
Name:Laptop company:Acer price:25000
Name:Laptop company:Dell price:45000

您还可以对多个字段进行排序。此代码将为您提供按公司升序排列的价目表。

for product in products.objects.order_by('company','price'):
   print ("Name:{} company:{} price:{}".format(product.Name, product.company, product.price))

输出

Name:Laptop company:Acer price:25000
Name:Scanner company:Cannon price:5000
Name:Printer company:Cannon price:12500
Name:Laptop company:Dell price:45000
Name:Router company:Iball price:2000
Name:TV company:Philips price:31000
Name:TV company:Samsung price:50000