Edge#

Manager/QuerySet Methods#

None

Methods used for building/manipulating#

None

Methods returning a QuerySet of Nodes#

None

Methods returning a QuerySet of Edges#

ancestor_edges(target_node)#

All Edge instances which are ancestors of the target Node.

:param Node target_node: The target Node for searching :return: Ancestor Edges :rtype: QuerySet

descendant_edges(target_node)#

All Edge instances descended from the target Node.

:param Node target_node: The target Node for searching :return: Descendant Edges :rtype: QuerySet

clan_edges(target_node)#

All Edge instances which are ancestors, self, and descendants of the target Node.

:param Node target_node: The target Node for searching :return: Clan Edges :rtype: QuerySet

shortest_path_edges(node_from, node_to)#

All Edge instances for the shortest path from node_from to node_to.

:param Node node_from: The starting Node :param Node node_to: The ending Node :return: Shortest path Edges :rtype: QuerySet

all_path_edges(node_from, node_to)#

All Edge instances for all paths from node_from to node_to.

:param Node node_from: The starting Node :param Node node_to: The ending Node :return: Edges :rtype: QuerySet

Methods returning a Boolean#

path_is_valid()#

Verify that the current QuerySet of Edges result in a contiguous path.

:rtype: bool

Methods returning other values#

from_node_queryset(nodes)#

Returns all Edge instances where a parent and child Node are within the provided QuerySet of Nodes.

:param QuerySet nodes: Nodes of interest :return: Edges with both parent and child Nodes in the provided QuerySet of Nodes :rtype: QuerySet

sorted()#

Sorts the current Edge QuerySet in a rootward direction

:return: Sorted Edges :rtype: QuerySet

Model Methods#

Methods used for building/manipulating an instance#

add_edge(from_node, to_node)#

Adds an edge between two Node instances.

:param Node node_from: The starting Node :param Node node_to: The ending Node :return: Newly created Edge :rtype: Edge

insert_node(node, clone_to_rootside=False, clone_to_leafside=False, pre_save=None, post_save=None)#

Insert a Node into an existing Edge instance.

:param Node node: The Node to insert :param bool clone_to_rootside: (optional) Clone properties of the existing Edge to the new rootside Edge :param bool clone_to_leafside: (optional) Clone properties of the existing Edge to the new leafside Edge :param callable pre_save: (optional) Helper function to modify before saving :param callable post_save: (optional) Helper function to modify after saving :return: Newly created rootside Edge (parent to the inserted node) and leafside Edge (child to the inserted Node) :rtype: tuple

Process:

  1. Add a new Edge from the parent Node of the current Edge instance to the provided Node instance, optionally cloning properties of the existing Edge.

  2. Add a new Edge from the provided Node instance to the child Node of the current Edge instance, optionally cloning properties of the existing Edge.

  3. Remove the original Edge instance.

The instance will still exist in memory, though not in database (https://docs.djangoproject.com/en/3.1/ref/models/instances/#refreshing-objects-from-database). Recommend running the following after conducting the deletion:

del instancename

Cloning will fail if a field has unique=True, so a pre_save function can be passed into this method. Likewise, a post_save function can be passed in to rebuild relationships. For instance, if you have a name field that is unique and generated automatically in the model’s save() method, you could pass in a the following pre_save function to clear the name prior to saving the new Edge instance(s):

def pre_save(new_edge):
    new_edge.name = ""
    return new_edge

A more complete example, where we have models named DAGEdge & DAGNode, and we want to insert a new Node (n2) into Edge e1, while copying e1’s field properties (except name) to the newly created rootside Edge instance (n1 to n2) is shown below.

Original        Final

n1  o           n1  o
    |                 \
    |                  o n2
    |                 /
n3  o           n3  o

from myapp.models import DAGEdge, DAGNode

n1 = DAGNode.objects.create(name="n1")
n2 = DAGNode.objects.create(name="n2")
n3 = DAGNode.objects.create(name="n3")

# Connect n3 to n1
n1.add_child(n3)

e1 = DAGEdge.objects.last()

# function to clear the `name` field, which is autogenerated and must be unique
def pre_save(new_edge):
    new_edge.name = ""
    return new_edge

DAGEdge.objects.insert_node(e1, n2, clone_to_rootside=True, pre_save=pre_save)

Methods returning a QuerySet of Nodes#

None

Methods returning a QuerySet of Edges#

None

Methods returning a Boolean#

None

Methods returning other values#

None