如何使用py2neo檢查NEO4J中是否存在節點

Question

我想在我的python代碼中插入以下驗證：

{`if (data.screen_name == node.screen_name) THEN {just create new relationship with new text} else {create new node with new relationship to text } `}

我需要在我的源代碼中實現此算法

Answer 1

選項1

首先使用.find（）查找節點（假設您使用帶標簽的neo4j 2.x）：

mynode = list(graph_db.find('mylabel', property_key='screen_name',
              property_value='foo'))

檢查是否發現了一些問題：

your_target_node = # you didn't specify where your target node comes from

# node found
if len(mynode) > 0:
    # you have at least 1 node with your property, add relationship
    # iterate if it's possible that you have more than 
    # one node with your property

    for the_node in mynode:
        # create relationship
        relationship = graph_db.create(
            (the_node, "LABEL", your_target_node, {"key": "value"})
        )

# no node found     
else:
    # create the node
    the_node, = graph_db.create({"key", "value"})

    # create relationship
    relationship = graph_db.create(
        (the_node, "LABEL", your_target_node, {"key": "value"})
    )

選項2

另外，請查看get_or_create_path（）以避免查找節點。 但是然后您必須知道您的節點，並且需要一個作為py2neo Node實例。 如果您始終知道/擁有目標節點並想要創建起始節點，則此方法可能會起作用：

path = one_node_of_path.get_or_create_path(
    "rel label",   {"start node key": start node value},
)

Answer 2

使用最新版本的Py2Neo：

from py2neo import Graph, NodeMatcher
graph = Graph(url) #along with username and password
def nodeExist(lbl, node):
    matcher = NodeMatcher(graph)
    m = matcher.match(lbl, screen_name == node.screen_name).first()
    if m is None:
       return False
    else:
       return True