python-3.x - py2neo v3 属性错误 : object has no attribute 'db_exists'

Question

尝试使用 py2neo 版本 3 将数据导入到一个干净的 Neo4j 图形数据库中。我定义了几个节点类型，如下所示，一切似乎都很顺利——除了我没有看到节点显示在我的 neo4j 浏览器中。

这是相关的导入代码；我已经验证记录正确加载到 Python 变量中。

for row in data:    
    ds = DataSource()
    #   parse Source of Information column as a list, trimming whitespace
    ds.uri = list(map(str.strip, row['data_source'].split(',')))
    ds.description = row['data_source_description']
    graph.merge(ds)

但是当我尝试做 graph.exists(ds) ，我得到了以下一组错误/回溯:

Traceback (most recent call last):
  File "mydir/venv/lib/python3.5/site-packages/py2neo/database/__init__.py", line 1139, in exists
    return subgraph.__db_exists__(self)
AttributeError: 'DataSource' object has no attribute '__db_exists__'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File     "mydir/venv/lib/python3.5/site-packages/py2neo/database/__init__.py", line 478, in exists
    return self.begin(autocommit=True).exists(subgraph)
  File "mydir/venv/lib/python3.5/site-packages/py2neo/database/__init__.py", line 1141, in exists
    raise TypeError("No method defined to determine the existence of object %r" % subgraph)
TypeError: No method defined to determine the existence of object <DataSource uri=['my_uri']>

令我惊讶的是，我找不到其他论坛帖子讨论这个问题。我猜是从 GraphObject 继承的问题，但是 there doesn't seem to be an explicit definition of a __db_exists__ property for GraphObject ， 任何一个。事实上，我唯一能找到提到的属性(property)的地方是 definition of the exists function ，当它产生这个错误时。

谁能看到我在这里做错了什么？

节点类定义如下:

class Content(GraphObject):             # group Person and Institution
    pass

class Person(Content):
    __primarykey__ = 'name'

    name = Property()
    in_scholar_names = Property()
#   
    mentored = RelatedTo('Person')
    mentored_by = RelatedFrom('Person', 'MENTORED')
    worked_alongside = Related('Person', 'WORKED_ALONGSIDE')
    studied_at = RelatedTo('Institution')
    worked_at = RelatedTo('Institution')
    tagged = RelatedTo('Tag')
    member_of = RelatedTo('Institution')

    last_update = RelatedTo('UpdateLog')

    def __lt__(self, other):
        return self.name.split()[-1] < other.name.split()[-1]

class Institution(Content):
    __primarykey__ = 'name'
#   
    name = Property()
    location = Property()
    type = Property()
    carnegie_class = Property()
#   
    students = RelatedFrom('Person', 'STUDIED_AT')
    employees = RelatedFrom('Person', 'WORKED_AT')
    members = RelatedFrom('Person', 'MEMBER_OF')

    last_update = RelatedTo('UpdateLog')

    def __lt__(self, other):
        return self.name < other.name


class User(GraphObject):
    __primarykey__ = 'username'

    username = Property()
    joined = Property()
    last_access = Property()
    active = Property()

    contributed = RelatedTo('UpdateLog')


class Provenance(GraphObject):          # group UpdateLog and DataSource
    pass    
# 
class UpdateLog(Provenance):
    __primarykey__ = 'id'

    id = Property()
    timestamp = Property()
    query = Property()

    previous = RelatedTo('UpdateLog', 'LAST_UPDATE')
    next = RelatedFrom('UpdateLog', 'LAST_UPDATE')
    based_on = RelatedTo('Provenance', 'BASED_ON')

    affected_nodes = RelatedFrom('Content', 'LAST_UPDATE')
    contributed_by = RelatedFrom('User', 'CONTRIBUTED')

class DataSource(Provenance):
    __primarykey__ = 'uri'

    id = Property()
    description = Property()
    uri = Property()

    source_for = RelatedFrom('UpdateLog', 'BASED_ON')


class Tag(GraphObject):
    __primarykey__ = 'name'

    name = Property()
    description = Property()

    see_also = Related('Tag')
    tagged = RelatedFrom('Content')

Answer 1

好吧，我想我想通了。我一直在 Flask 的上下文中学习 py2neo，其中所有这些类定义对于生成给定节点上的关系的 View (网页)都很重要和有用。

但是对于我目前正在编写的数据导入脚本，即首先要实际创建节点和关系，我需要使用“节点”和“关系”的原版类，并且只需将类型指定为参数功能。上面原始代码的这个更新版本不会产生错误，并且 graph.exists(ds)返回 true之后:

for row in data:    
    ds = Node("DataSource")
    #   parse Source of Information column as a list, trimming whitespace
    ds['uri'] = list(map(str.strip, row['data_source'].split(',')))
    ds['description'] = row['data_source_description']
    graph.merge(ds)

另外两个值得注意的发现:

我的类继承一开始就不合时宜，因为我应该尝试从 Node 继承。 ，不是 GraphObject (尽管 GraphObject 是在 Flask 上下文中继承的正确类)

对于 Node类，我必须使用 dict 样式的属性分配，方括号和键名作为带引号的字符串；点符号在这里偏离了基础，我很惊讶我没有抛出更多错误，而且更快。