py2neo存在返回错误结果

Question

when i use py2neo exists() i get a wrong result,i think the result will be 'True',but it give a 'False' when i use

c = Node("Person", name="Alice")
g.exists(c)

it return a 'False', but when i change like this

c = a
g.exists(c)

i will get a 'True' why?

from py2neo import Graph,Node,Relationship
g = py2neo.Graph('http://localhost:7474', user='yudeng',password='yudeng')
a = Node("Person", name="Alice")
b = Node("Person", name="Bob")
ab = Relationship(a, "KNOWS", b)
print(a)
g.create(a)
g.create(b)
g.create(ab)
c = Node("Person", name="Alice")
g.exists(c)

Answer 1

When you just state

c = Node("Person", name="Alice")
g.exists(c)

Result:

False

without

g.create(c)

Then the node does not exist because you did not created the node in the graph.

This is what you executed to get a True:

a = Node("Person", name="Alice")
b = Node("Person", name="Bob")
ab = Relationship(a, "KNOWS", b)
print(a)
g.create(a)
g.create(b)
g.create(ab)
c = a
g.exists(c)

Because then c equals to a that means the node exists => Node("Person", name="Alice") can then be found with a and c.

Result:

(:Person {name: 'Alice'})

True