[Neo4j系列十四]Neo4j的python操作库Neomodel

neomodel是neo4j数据库的OGM(Object Graph Mapper)的python库，基于neo4j_driver开发。当在开发过程中需要查询节点的属性时，用这个库就会非常方便，也使代码简洁流畅。

1. 安装neonodel的Python包

• pypi源安装

  pip install neomodel

• 从github安装

  pip install git+git://github.com/neo4j-contrib/neomodel.git@HEAD#egg=neomodel-dev

2. 连接neo4j数据库

• config配置

  from neomodel import config
  config.DATABASE_URL = 'bolt://neo4j:neo4j@localhost:7687'  # default

• db配置

  from neomodel import db
  db.set_connection('bolt://neo4j:neo4j@localhost:7687')

3. Nodes

• 通过StructuredNode构建映射节点类

  from neomodel import (config, StructuredNode, StringProperty, IntegerProperty,
  UniqueIdProperty, RelationshipTo, RelationshipFrom)
  config.DATABASE_URL = 'bolt://neo4j:password@localhost:7687'
  class Country(StructuredNode):
      code = StringProperty(unique_index=True, required=True)# traverse incoming IS_FROM relation, inflate to Person objects
      inhabitant = RelationshipFrom('Person', 'IS_FROM')
  class Person(StructuredNode):
      uid = UniqueIdProperty()
      name = StringProperty(unique_index=True)
      age = IntegerProperty(index=True, default=0)
  # traverse outgoing IS_FROM relations, inflate to Country objects
  country = RelationshipTo(Country, 'IS_FROM')

  Country和Person节点类都是继承StructuredNode构建的，节点类的属性通过实例化不同的数据类构建，这些属性也只是我们自己创建的节点属性，与neo4j自己生成的节点属性无关，比如id，labels等。

• Create, Save, Delete操作
  实例化节点、属性赋值、保存、删除、重载、等

  jim = Person(name='Jim', age=3).save()
  jim.age = 4jim.save() 
  # validation happens here
  jim.delete()
  jim.refresh() 
  # reload properties from neo
  jim.id 
  # neo4j internal id

• 查找节点
  使用“.nodes”类属性查找节点，根据条件筛选节点

  # raises Person.DoesNotExist if no match
  jim = Person.nodes.get(name='Jim')
  # Will return None unless bob exists
  someone = Person.nodes.get_or_none(name='bob')
  # Will return the first Person node with the name bob. This raises Person.DoesNotExist if there's no match.
  someone = Person.nodes.first(name='bob')
  # Will return the first Person node with the name bob or None if there's no match
  someone = Person.nodes.first_or_none(name='bob')
  # Return set of nodes
  people = Person.nodes.filter(age__gt=3)
  

4. Relationships

• 使用StructuredRel构建映射边的类

  class FriendRel(StructuredRel):
      since = DateTimeProperty(
      default=lambda: datetime.now(pytz.utc)
  )
      met = StringProperty()
  

• class Person(StructuredNode):
      name = StringProperty()
      friends = RelationshipTo('Person', 'FRIEND', model=FriendRel)
  rel = jim.friends.connect(bob)
  rel.since # datetime object

  通过Relationship构建两个类之间无向的关系，通过RelationshipTo或RelationshipFrom构建类之间有向关系，通过model指定关系实例继承的类，继承相关的属性。

• 基数限制
  如果对边加上基数限制，需要在边的两个方向上分别去做定义，对cardinality作设置。

  class Person(StructuredNode):
      car = RelationshipTo('Car', 'OWNS', cardinality=One)
  

  class Car(StructuredNode):
      owner = RelationshipFrom('Person', 'OWNS', cardinality=One)

• 实例化及常用方法

  rel = jim.friends.connect(bob,
                       {'since': yesterday, 'met': 'Paris'})
  print(rel.start_node().name) 
  # jim
  print(rel.end_node().name) 
  # bob
  rel.met = "Amsterdam"rel.save()

  通过connect方法实例化一条边，还可以指定属性筛选；
  通过start_node、end_node可以查看边的属性；
  还可以对边进行赋值，并保存。
  此外，当两个节点存在一种关系时，则可以使用relationship这种方法

  rel = jim.friends.relationship(bob)

5. Property types

属性默认值设置，可以是具体值，也可以是函数

from uuid import uuid4
my_id = StringProperty(unique_index=True, default=uuid4)
my_datetime = DateTimeProperty(default=lambda: datetime.now(pytz.utc))

StringProperty 的Choices

class Person(StructuredNode):
    SEXES = {'F': 'Female', 'M': 'Male', 'O': 'Other'}
    sex = StringProperty(required=True, choices=SEXES)
tim = Person(sex='M').save()
tim.sex # M
tim.get_sex_display() # 'Male'

• Array Properties

  class Person(StructuredNode):
     names = ArrayProperty(StringProperty(), required=True)
  bob = Person(names=['bob', 'rob', 'robert']).save()

• UniqueIdProperty

  class Person(StructuredNode):
      uid = UniqueIdProperty()
  Person.nodes.get(uid='a12df...')

• Dates and times
  DateTimeProperty 对应 UTC epoch value
  DateProperty 对应‘YYYY-MM-DD’

  created = DateTimeProperty(default_now=True)

  -Aliasing properties
  依赖属性支持节点属性设置

  class Person(StructuredNode):
      full_name = StringProperty(index=True)
      name = AliasProperty(to='full_name')
  Person.nodes.filter(name='Jim') # just works

• 独特属性名
  使用db_property去创建属性，类似于创建类属性

  class Person(StructuredNode):
      name_ = StringProperty(db_property='name')
      @property
      def name(self):
          return self.name_.lower() if self.name_ else None
      @name.setter
      def name(self, value):
          self.name_ = value

• Other properties
  EmailProperty、RegexProperty、NormalProperty

1. Advanced queries

• 节点集合与过滤
  通过nodes属性获得节点集合，通过filter过滤节点

  class SupplierRel(StructuredRel):
      since = DateTimeProperty(default=datetime.now)
  class Supplier(StructuredNode):
      name = StringProperty()
      delivery_cost = IntegerProperty()
      coffees = RelationshipTo('Coffee', 'SUPPLIES')
  class Coffee(StructuredNode):
      name = StringProperty(unique_index=True)
      price = IntegerProperty()
      suppliers = RelationshipFrom(Supplier, 'SUPPLIES', model=SupplierRel)
  # nodes with label Coffee whose price is greater than 2Coffee.nodes.filter(price__gt=2)
  try:
      java = Coffee.nodes.get(name='Java')
  except Coffee.DoesNotExist:
      print "Couldn't find coffee 'Java'"

  过滤的方法有以下：
  lt - less than
  gt - greater than
  lte - less than or equal to
  gte - greater than or equal to
  ne - not equal
  in - item in list
  isnull - True IS NULL, False IS NOT NULL
  exact - string equals
  iexact - string equals, case insensitive
  contains - contains string value
  icontains - contains string value, case insensitive
  startswith - starts with string value
  istartswith - starts with string value, case insensitive
  endswith - ends with string value
  iendswith - ends with string value, case insensitive
  regex - matches a regex expression
  iregex - matches a regex expression, case insensitive

• 查看具有关系
  利用has方法查看节点是否有一种或多种方法，True 为有，False为无

  Coffee.nodes.has(suppliers=True)

• 迭代性、切片、计数等

  # Iterable
  for coffee in Coffee.nodes:
      print coffee.name
  # Sliceable using python slice syntax
  coffee = Coffee.nodes.filter(price__gt=2)[2:]
  # Count with __len__
  print len(Coffee.nodes.filter(price__gt=2))
  if Coffee.nodes:
      print "We have coffee nodes!"
  

• 过滤关系
  使用match方法过滤关系

  nescafe = Coffee.nodes.get(name="Nescafe")
  for supplier in nescafe.suppliers.match(since_lt=january):  
      print supplier.name

• 通过属性排序
  使用order_by方法排序，加’-‘倒排

  # Ascending sort
  for coffee in Coffee.nodes.order_by('price'):
      print coffee, coffee.price
  # Descending sort
  for supplier in Supplier.nodes.order_by('-delivery_cost'):
      print supplier, supplier.delivery_cost

• 指定None则不排序，使用’？’随机排序

  # Sort in descending order
  suppliers = Supplier.nodes.order_by('-delivery_cost')
  # Don't order; yield nodes in the order neo4j returns them
  suppliers = suppliers.order_by(None)
  

  Coffee.nodes.order_by('?')

7. Cypher queries

• 通过StructuredNode的inflate类方法实现cypher查询

  class Person(StructuredNode):
    def friends(self):
        results, columns = self.cypher("MATCH (a) WHERE id(a)={self} MATCH (a)-[:FRIEND]->(b) RETURN b")      
        return [self.inflate(row[0]) for row in results]

• StructuredNode外构建cypher

  # for standalone queries
  from neomodel import db
  results, meta = db.cypher_query(query, params)
  people = [Person.inflate(row[0]) for row in results]

  参考链接：https://neomodel.readthedocs.io/en/latest/index.html