PyMongo是一个低级的MongoDB的Python驱动器（我一般称为客户端），它封装了 MongoDB API，并通过JSON与MongoDB通信，PyMongo将MongoDB的数据映射成Python的内置类型。
MongoEngine 是一个Document-Object Mapper (想一下ORM, 但它是针对文档型数据库)，Python通过它与MongoDB交互。你可能会说那PyMongo也是ORM啊，在Python中一切都是对象，但我们所说的ORM中的Object在指Python中的自定义类，而不是内置类型。MongoEngine或MongoKit将MongoDB的数据映射成自定义类实例，它们都是基于PyMongo的。
我们可以跟关系型数据库的Python客户端MySQLdb，以及ORM SQLAlchemy/Django ORM比较一下，PyMongo相当于MySQLdb，MongoEngine相当于SQLAlchemy，SQLAlchemy是基于MySQLdb之上的，MongoEngine是基于PyMongo的。
MongoEngine是一个ORM

安装

pip install mongoengine

连接

from mongoengine import * 
connect(‘mongoengine_test’,host=’localhost’,port=27017)

定义文档中的存放数据的字段,还要继承Document类,在这里定义好模型限制,以后save的时候做验证用得着

import datetime

class Post(Document):
    title = StringField(required=True, max_length=200)
    content = StringField(required=True)
    author = StringField(required=True, max_length=50)
    published = DateTimeField(default=datetime.datetime.now)

required：设置必须；

default：如果没有其他值给出使用指定的默认值

unique：确保集合中没有其他document有此字段的值相同

choices：确保该字段的值等于数组中的给定值之一

4.完整的插入保存过程

from mongoengine import *

connect('mongoengine_test',host='localhost',port=27017)

import datetime

class Post(Document):
title = StringField(required=True, max_length=200)
content = StringField(required=True)
author = StringField(required=True, max_length=50)
published = DateTimeField(default=datetime.datetime.now)

post_1 = Post(
title='Sample Post',
content='Some engaging',
author='scott'
)
post_1.save()
print(post_1.title)

post_1.title = '张昆'

post_1.save()
print(post_1.title)

mongoengine基本用法实例：

from mongoengine import *
from datetime import datetime

#连接数据库:test
# connect('test')    # 连接本地test数据库
connect('test', host='127.0.0.1', port=27017, username='test', password='test')

# Defining our documents
# 定义文档user,post,对应集合user,post
class User(Document):
    # required为True则必须赋予初始值
    email = StringField(required=True)
    first_name = StringField(max_length=50)
    last_name = StringField(max_length=50)
    date = DateTimeField(default=datetime.now(), required=True)

# Embedded documents,it doesn’t have its own collection in the database
class Comment(EmbeddedDocument):
    content = StringField()
    name = StringField(max_length=120)

class Post(Document):
    title = StringField(max_length=120, required=True)
    # ReferenceField相当于foreign key
    author = ReferenceField(User)
    tags = ListField(StringField(max_length=30))
    comments = ListField(EmbeddedDocumentField(Comment))
    # 允许继承
    meta = {'allow_inheritance': True}

class TextPost(Post):
    content = StringField()

class ImagePost(Post):
    image_path = StringField()

class LinkPost(Post):
    link_url = StringField()

# Dynamic document schemas:DynamicDocument documents work in the same way as Document but any data / attributes set to them will also be saved
class Page(DynamicDocument):
    title = StringField(max_length=200, required=True)
    date_modified = DateTimeField(default=datetime.now())

添加数据

john = User(email='john@example.com', first_name='John', last_name='Tao').save()
ross = User(email='ross@example.com')
ross.first_name = 'Ross'
ross.last_name = 'Lawley'
ross.save()

comment1 = Comment(content='Good work!',name = 'LindenTao')
comment2 = Comment(content='Nice article!')
post0 = Post(title = 'post0',tags = ['post_0_tag'])
post0.comments = [comment1,comment2]
post0.save()

post1 = TextPost(title='Fun with MongoEngine', author=john)
post1.content = 'Took a look at MongoEngine today, looks pretty cool.'
post1.tags = ['mongodb', 'mongoengine']
post1.save()

post2 = LinkPost(title='MongoEngine Documentation', author=ross)
post2.link_url = 'http://docs.mongoengine.com/'
post2.tags = ['mongoengine']
post2.save()

# Create a new page and add tags
page = Page(title='Using MongoEngine')
page.tags = ['mongodb', 'mongoengine']
page.save()

创建了三个集合:user,post,page

这里写图片描述 这里写图片描述 这里写图片描述

查看数据

# 查看数据
for post in Post.objects:
    print post.title
    print '=' * len(post.title)

    if isinstance(post, TextPost):
        print post.content

    if isinstance(post, LinkPost):
        print 'Link:', post.link_url

# 通过引用字段直接获取引用文档对象    
for post in TextPost.objects:
    print post.content
    print post.author.email  
au = TextPost.objects.all().first().author
print au.email

# 通过标签查询    
for post in Post.objects(tags='mongodb'):
    print post.title   
num_posts = Post.objects(tags='mongodb').count()
print 'Found %d posts with tag "mongodb"' % num_posts

# 多条件查询(导入Q类) 
User.objects((Q(country='uk') & Q(age__gte=18)) | Q(age__gte=20))   

# 更新文档
ross = User.objects(first_name = 'Ross')
ross.update(date = datetime.now())
User.objects(first_name='John').update(set__email='123456@qq.com')
//对 lorem 添加商品图片信息
lorempic = GoodsPic(name='l2.jpg', path='/static/images/l2.jpg')
lorem = Goods.objects(id='575d38e336dc6a55d048f35f')
lorem.update_one(push__pic=lorempic)
# 删除文档
ross.delete()

备注

ORM全称“Object Relational Mapping”，即对象-关系映射，就是把关系数据库的一行映射为一个对象，也就是一个类对应一个表，这样，写代码更简单，不用直接操作SQL语句。

链接：

https://blog.csdn.net/u011845833/article/details/51151434
https://blog.csdn.net/u013205877/article/details/76037540

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