连接Neo4j数据库

要通过python来操作Neo4j，
首先需要安装py2neo，可以直接使用pip安装。
需要注意的是如果使用默认的pip install py2neo则在进行create node时会出现报错问题，因此需选择合适的版本。
我选用的版本是Neo4j—3.3.1、py2neo—4.0.0、python3.4

pip3 install py2neo

在完成安装之后，在python中调用py2neo即可，常用的有Graph,Node,Relationship。

from py2neo import Graph,Node,Relationship
连接Neo4j的方法很简单：
test_graph = Graph( "http://localhost:7474", username="neo4j", password="neo4j" )
test_graph就是我们建立好的Neo4j的连接。
Neo4j的服务器装好了之后，默认的端口号就是7474,所以本地的主机就是"http://localhost:7474" 。

程序代码及注释如下

# -*- coding: utf-8 -*-
 
from py2neo import Graph, Node, Relationship, NodeSelector
 
graph = Graph("http://localhost:7474", username="neo4j", password='password')
graph.delete_all()
 
'''
    1 —— 创建node，函数第一个参数是节点类型，第二个参数是value值
'''
a = Node('PersonTest', name='张三')
b = Node('PersonTest', name='李四')
r = Relationship(a, 'KNOWNS', b)
s = a | b | r
graph.create(s)
 
'''
    2　——　Node查询
'''
# 用CQL进行查询，返回的结果是list
data1 = graph.data('MATCH(p:PersonTest) return p')
print("data1 = ", data1, type(data1))
print()
# 用find_one()方法进行node查找，返回的是查找node的第一个node
data2 = graph.find_one(label='PersonTest', property_key='name', property_value="李四")
print( "data2 = ", data2, type(data2))
print()
# 用find()方法进行node查找
data3 = graph.find(label='PersonTest')
for data in data3:
    print( "data3 = ", data)
print()
'''
    3　——　Relationship查询
'''
relationship = graph.match_one(rel_type='KNOWNS')
print( relationship, type(relationship))
print()
 
'''
    4 —— 更新Node的某个属性值，若node没有该属性，则新增该属性
'''
node1 = graph.find_one(label='PersonTest', property_key='name', property_value="张三")
node1['age'] = 21
graph.push(node1)
data4 = graph.find(label='PersonTest')
for data in data4:
    print( "data4 = ", data)
print()
 
node1['age'] = 99
graph.push(node1)
data5 = graph.find(label='PersonTest')
for data in data5:
    print( "data5 = ", data)
print()
 
'''
    5 —— 删除某node，在删除node之前需要先删除relationship
'''
node = graph.find_one(label='PersonTest', property_key='name', property_value="李四")
relationship = graph.match_one(rel_type='KNOWNS')
graph.delete(relationship)
graph.delete(node)
data6 = graph.find(label='PersonTest')
for data in data6:
    print( "data6 = ", data)
 
'''
    6 —— 多条件查询
'''
a = Node('PersonTest', name='张三', age=21, location='广州')
b = Node('PersonTest', name='李四', age=22, location='上海')
c = Node('PersonTest', name='王五', age=21, location='北京')
r1 = Relationship(a, 'KNOWS', b)
r2 = Relationship(b, 'KNOWS', c)
s = a | b | c | r1 | r2
graph.create(s)
data7 = graph.find(label='PersonTest')
for data in data7:
    print( "data7 = ", data)
print()
 
# 单条件查询，返回的是多个结果
selector = NodeSelector(graph)
persons = selector.select('PersonTest', age=21)
print("data8 = ", list(persons))
print()
 
# 多条件查询
selector = NodeSelector(graph)
persons = selector.select('PersonTest', age=21, location='广州')
print("data9 = ", list(persons))
print()
 
# orderby进行更复杂的查询
selector = NodeSelector(graph)
persons = selector.select('PersonTest').order_by('_.age')
for data in persons:
    print( "data10 = ", data)
print()