py2neo:无法创建图形

Question

我想尝试一下py2neo，但甚至不能使用文档中的代码示例。请参见here示例。代码是：

from py2neo import Graph, Node, Relationship
g = Graph()
tx = g.begin()
a = Node("Person", name="Alice")
tx.create(a)
b = Node("Person", name="Bob")
ab = Relationship(a, "KNOWS", b)
tx.create(ab)
tx.commit()
g.exists(ab)

这将返回一些错误消息：

Traceback (most recent call last):
  File ".\test_py2neo.py", line 22, in <module>
    tx = g.begin()
  File "C:\Users\saran\AppData\Local\Programs\Python\Python35\lib\site-packages\py2neo\database.py", line 335, in begin
    return Transaction(self, autocommit)
  File "C:\Users\saran\AppData\Local\Programs\Python\Python35\lib\site-packages\py2neo\database.py", line 797, in __init__
    self.transaction = self.session.begin_transaction()
AttributeError: 'NoneType' object has no attribute 'begin_transaction'
Exception ignored in: <bound method Driver.__del__ of <neo4j.v1.api.Driver object at 0x000001325C9F0940>>
Traceback (most recent call last):
  File "C:\Users\saran\AppData\Local\Programs\Python\Python35\lib\site-packages\neo4j\v1\api.py", line 151, in __del__
  File "C:\Users\saran\AppData\Local\Programs\Python\Python35\lib\site-packages\neo4j\v1\api.py", line 193, in close
AttributeError: 'str' object has no attribute 'close'

如果我理解的很好，API已经改变了，文档没有更新。但我使用的是版本4，而手册似乎是为该版本编写的。有什么可以帮助我入门的建议吗？

Answer 1

好吧，是我的错，我用错了py2neo。下面是一段适用于我的代码：

from py2neo import Graph, Node, Relationship

uri = "bolt://localhost:7687"
user = "neo4j"
password = "..."

g = Graph(uri=uri, user=user, password=password)

# optionally clear the graph
# g.delete_all()

print(len(g.nodes))
print(len(g.relationships))

# begin a transaction
tx = g.begin()

# define some nodes and relationships
a = Node("Person", name="Alice")
b = Node("Person", name="Bob")
ab = Relationship(a, "KNOWS", b)

# create the nodes and relationships
tx.create(a)
tx.create(b)
tx.create(ab)

# commit the transaction
tx.commit()

print(g.exists(ab))
print(len(g.nodes))
print(len(g.relationships))

显然，在执行此代码之前，Neo4j服务器必须已启动并运行。