知识图谱学习（一） py2neo

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一、python 与neo4j 数据库交互

py2neo==4.3.0

1.创建图对象

from py2neo import Graph
'''
host:服务器ip地址，默认为'localhost'
http_port:http协议——服务器监听端口，默认7474
https_port:https协议——服务器监听端口，默认7473
user:登录用户名，默认'neo4j'
password:登录密码，无默认值，故若数据库其他参数都为默认值，则可直接通过密码登录
'''
graph = Graph('http://localhost:7474', auth=("neo4j", "123456"))
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2.创建数据对象

Relationship

from py2neo import Graph, Node, Relationship

g = Graph('http://localhost:7474', username='neo4j', password='123456')
a = Node('Person', name='Alice')
b = Node('Person', name='Bob')
ab = Relationship(a, 'KNOWS', b)
g.create(ab)
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query

# 新版
from py2neo import Graph, Node, Relationship, Subgraph

g = Graph('http://localhost:7474', username='neo4j', password='123456')

tx = g.begin()
jiazhen = Node("Person", name="陈家珍", age=66)
fugui = Node("Person", name='徐福贵', age=67)
youqian = Node("Person", name="徐有钱")
renxing = Node("Person", name="徐任性")

cat = Node("Person", name='cat')
dog = Node("Person", name='dog')

wife = Relationship(fugui, "WIFE", jiazhen)
brother_1 = Relationship(fugui, "BROTHER", youqian)
brother_2 = Relationship(fugui, "BROTHER", renxing)
hus = Relationship(jiazhen, 'HUS', fugui)
know = Relationship(cat, 'KNOWS', dog)

relation_list = Subgraph(relationships=[wife, brother_2, brother_1, hus, know])

tx.create(relation_list)
tx.commit()
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匹配所有节点

from py2neo import Graph, Node, Relationship

g = Graph('http://localhost:7474', auth=("neo4j", "123456"))

nodes = g.nodes.match()

for node in nodes:
    print(node)
print(node.items())
print(node.labels)
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匹配符合指定条件节点

from py2neo import Graph, Node, Relationship, NodeMatcher

g = Graph('http://localhost:7474', auth=("neo4j", "123456"))

# 用来查找节点的对象
matcher = NodeMatcher(g)

# first 返回第一个符合条件的节点
# node1 = matcher.match('Person', name='徐有钱').first()
node1 = matcher.match('Person').where("_.name='徐有钱'").first()
print(node1)

# all 返回所有符合条件的节点
nodes = matcher.match('Person')

for node in nodes:
    print('姓名：%s \t 年龄：%s '% (node['name'], node['age']))

nodes = matcher.match('Person').where("_.age=66")
print('*' * 25 + '年龄66的节点' + '*' * 25)
for node in nodes:
    print('姓名：%s \t 年龄：%s ' % (node['name'], node['age']))

# 模糊匹配 要用Cypher
nodes = matcher.match("Person").where("_.name =~ '徐.*'")

print('*' * 25 + '姓徐的节点' + '*' * 25)
for node in nodes:
    print('姓名：%s \t 年龄：%s ' % (node['name'], node['age']))
    
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Update

py2neo==2020.1.0

本来想继续使用py2neo==4.3.0版本，无奈总是报错，针对该错误的情况的代码修改方式较少，更多的推荐是更改py2neo版本。

修改单个节点

from py2neo import Graph, Node, Relationship, NodeMatcher, Subgraph

g = Graph('http://localhost:7474', auth=("neo4j", "123456"))

from py2neo import Graph, NodeMatcher

tx = g.begin()
# 找到你要找的Nodes
matcher = NodeMatcher(g)

# 修改单个节点
init_node = matcher.match("Person").where('_.name="徐福贵"')
new_node = init_node.first()
new_node['name'] = "福贵"
sub = Subgraph(nodes=[new_node])
tx.push(sub)
tx.commit()
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修改多个节点

# 修改多个节点
from py2neo import Graph, Node, Relationship, NodeMatcher, Subgraph

g = Graph('http://localhost:7474', auth=("neo4j", "123456"))

from py2neo import Graph, NodeMatcher

tx = g.begin()
# 找到你要找的Nodes
matcher = NodeMatcher(g)

init_node = matcher.match("Person")
new_nodes = []
for node in init_node.all():
    node['name'] = '⭐'+node['name']
    new_nodes.append(node)

sub = Subgraph(nodes=new_nodes)
tx.push(sub)
tx.commit()
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两个节点新加关系

from py2neo import Graph, Node, Relationship, NodeMatcher, Subgraph

g = Graph('http://localhost:7474', auth=("neo4j", "123456"))

matcher = NodeMatcher(g)

fugui = matcher.match('Person', name='⭐福贵').first()
youqian = matcher.match('Person', name='⭐徐有钱').first()

relation = Relationship(fugui, 'Brother', youqian)

g.create(relation)
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删除

删除关系链 delete

节点也会被删除

from py2neo import Graph, Node, Relationship, NodeMatcher, Subgraph, RelationshipMatcher

g = Graph('http://localhost:7474', auth=("neo4j", "123456"))

matcher = NodeMatcher(g)
r_matcher = RelationshipMatcher(g)
a = matcher.match('Person', name='⭐Alice').first()
b = matcher.match('Person', name='⭐Bob').first()

relation = r_matcher.match(nodes=[a, b]).first()	#也可以是none,表示任意节点。注意前后顺序
# nodes=[None,b] 表示所有以b为终点的关系
# nodes=[a,None] 表示所有以a为起点的关系
# nodes=[None,None] 表示所有节点的关系
print(relation)
g.delete(relation)
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只删除关系 separate

from py2neo import Graph, Node, Relationship, NodeMatcher, Subgraph, RelationshipMatcher

g = Graph('http://localhost:7474', auth=("neo4j", "123456"))

matcher = NodeMatcher(g)
r_matcher = RelationshipMatcher(g)
cat = matcher.match('Person', name='⭐cat').first()
dog = matcher.match('Person', name='⭐dog').first()

relation = r_matcher.match(nodes=[cat, dog]).first()
print(relation)
g.separate(relation)
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批处理

创建多个节点

from py2neo import Graph, Node, Relationship, NodeMatcher, Subgraph, RelationshipMatcher

g = Graph('http://localhost:7474', auth=("neo4j", "123456"))

tx = g.begin()
node_list = [Node("Num", name=str(i)) for i in range(4)]

node_list = Subgraph(nodes=node_list)

tx.create(node_list)
tx.commit()
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删除所有的关系

from py2neo import Graph, Node, Relationship, NodeMatcher, Subgraph, RelationshipMatcher

g = Graph('http://localhost:7474', auth=("neo4j", "123456"))
matcher = RelationshipMatcher(g)
tx = g.begin()
relationship_list = matcher.match().all()

node_list = Subgraph(relationships=relationship_list)

tx.separate(node_list)
tx.commit()
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二、版本问题

Neo4j版本4.2.1，Python版本3.6 的条件下 py2neo4.3.0版本无法使用

NodeMatcher(graph).match().all()
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py2neo4.0.0版本可使用NodeMatcher(graph).match().all()，但无法与当前版本的Neo4j建立连接

py2neo4.3.0版本可以使用

NodeMatcher(graph).match().first()
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py2neo4.3.0版本无法使用

node1 = matcher.match('Person', name='徐有钱').first()
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py2neo4.3.0版本可以使用

node1 = matcher.match('Person').where("_.name='徐有钱'").first()
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py2neo最新版本无法直接访问Neo4j，情况同py2neo4.0.0版本近似 py2neo3.1.2版本支持Python3.5以下版本

因此推荐使用py2neo 2020.1.0版本

三、参考链接

python 与neo4j 数据库交互
neo4j基本使用及其Python语言操作