py2neo-v2 merge_one, create_unique, find_one for py2neo v3 的等效方法有哪些？

Question

我最近从 version V2 to version V3 切换了我的 py2neo 库，但我不知道执行某些操作的新命令。

特别是我坚持：

graph.merge_one

Match or create a node by label and optional property and return a single matching node. This method is intended to be used with a unique constraint and does not fail if more than one matching node is found. (read the docs)

例如

from py2neo import Node, Graph
nicole = Node("Person", name="Nicole", age=24) 

# adds the nicole element to the graph if it does not already exist a node labelled as "Person" having attribute "name" equal to "Nicole".
graph.merge_one("Person", "name", "Nicole")     #<-- What's the equivalent py2neo V3 command?

graph.create_unique

Create one or more unique paths or relationships in a single transaction. This is similar to create() but uses a Cypher CREATE UNIQUE clause to ensure that only relationships that do not already exist are created. (read the docs)

例如

from py2neo import Node, Relationship, Graph

kenny = Node("Person", name="Kenny")
graph.create(kenny)

kingfish = Node("Bar", name="Kingfish")
graph.create(kingfish)

rel = Relationship(kenny, "LIKES", kingfish)

# creates the relationship (kenny)-[:LIKES]->(kingfish), but only if it does not exist yet.
graph.create_unique(rel)     #<-- What's the equivalent py2neo V3 command?

graph.find_one

Find a single node by label and optional property. This method is intended to be used with a unique constraint and does not fail if more than one matching node is found. (read the docs)

例如

from py2neo import Graph

# Find one node (and take only one if there are many) matching these conditions: its type is "Person" and it has an attribute "name" equal to "Kenny", and then save it inside "kenny" variable.
kenny = graph.find_one("Person", "name", "Kenny")      #<-- What's the equivalent py2neo V3 command?

我发现这些方法在py2neo V3中不再可用，
那么这些方法对于 py2neo V3 的等价物是什么？

Answer 1

这些是 py2neo V3 的等效方法（也适用于 py2neo V.2020.1）

• merge_one -> merge

• create_unique -> 在你的例子中它只是 merge，因为这 足以确保

  only relationships that do not already exist are created.

• find_one ->

  这更复杂，必须拆分成更多的操作，
  您可以使用 NodeMatcher 函数和 match 方法来完成。
  我将在下面的示例中直接显示它。

以下是您更改为 py2neo V3 命令的示例：

graph.merge_one

Match or create a node by label and optional property and return a single matching node. This method is intended to be used with a unique constraint and does not fail if more than one matching node is found. ([read the docs][3])

例如

from py2neo import Node, Graph
nicole = Node("Person", name="Nicole", age=24) 

# adds the nicole element to the graph if it does not already exist a node labelled as "Person" having attribute "name" and "Person" and having their values equal to those of "nicole" element.
graph.merge(nicole, "Person", "name") 

graph.create_unique

Create one or more unique paths or relationships in a single transaction. This is similar to create() but uses a Cypher CREATE UNIQUE clause to ensure that only relationships that do not already exist are created. ([read the docs][4])

例如

from py2neo import Node, Relationship, Graph

kenny = Node("Person", name="Kenny")
graph.create(kenny)

kingfish = Node("Bar", name="Kingfish")
graph.create(kingfish)

rel = Relationship(kenny, "LIKES", kingfish)

# creates the relationship (kenny)-[:LIKES]->(kingfish), but only if it does not exist yet.
graph.merge(rel)

graph.find_one

Find a single node by label and optional property. This method is intended to be used with a unique constraint and does not fail if more than one matching node is found. ([read the docs][5])

例如

from py2neo import Graph

# Find one node (and take only one if there are many) matching these conditions: its type is "Person" and it has an attribute "name" equal to "Kenny", and then save it inside "kenny" variable.
from py2neo import NodeMatcher
matcher = NodeMatcher(graph)
kenny = matcher.match('Person', name='Kenny').first()