Python中使用MongoEngine2

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

 

 

 

 

 

 

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。