How to Create a Graph using existing Collections (Documents and Edges)

After inspect the network flow from the WebGui, I found out that Add graph essentially is sending a json post request with Edge and Document connection name as string input. Thus, what is prevent us using existing edges and documents is the validation built default in pyarango

def _checkCollectionList(lst):
    for colName in lst:
        if not COL.isCollection(colName):
            raise ValueError("'%s' is not a defined Collection" % colName)

graphClass = GR.getGraphClass(name)

ed = []
for e in graphClass._edgeDefinitions:
    if not COL.isEdgeCollection(e.edgesCollection):
        raise ValueError("'%s' is not a defined Edge Collection" % e.edgesCollection)
    _checkCollectionList(e.fromCollections)
    _checkCollectionList(e.toCollections)

    ed.append(e.toJson())

_checkCollectionList(graphClass._orphanedCollections)

To overcome this issue, we only need to implement class first before create graph. for e.g., I have two documents collections people and department, and I want to create a graph which:

• people -> knowns -> people
• people -> belongs_to -> department

suppose I already have collection "people", "department", "knowns", "belongs_to" in my arangodb, the code to create a graph is as following:

from pyArango.collection import Collection, Field
from pyArango.graph import Graph, EdgeDefinition

class knowns(Edges):
    pass

class belongs_to(Edges):
    pass

class people(Collection):
    pass

class department(Collection):
    pass

# Here's how you define a graph
class MyGraph(Graph) :
    _edgeDefinitions = [EdgeDefinition('knowns', ['people'], ['people']),
                        EdgeDefinition('belongs_to', ['people'], ['department'])]
    _orphanedCollections = []

theGraph = arrango_db.createGraph(name="MyGraph", createCollections=False)

Be aware that the class name is exactly the same as the string I passed into graph creation. Now we have the graph created in ArangoDB:

Another solution, useful when you already have defined Nodes and Edges, is to dynamically create the classes with type:

from pyArango.graph import Graph, EdgeDefinition
from pyArango.collection import Collection, Edges

# generate the class for "knowns", inheriting class "Edges", etc. 
_ = type("knowns", (Edges,), {}) 
_ = type("belongs_to", (Edges,), {}) 
_ = type("people", (Collection,), {})
_ = type("department", (Collection,), {})

# finally generate the class for the graph
_ = type(attribute+'Graph', (Graph,), 
        {"_edgeDefinitions" : [EdgeDefinition('knowns', ['people'], ['people']),
                    EdgeDefinition('belongs_to', ['people'], ['department'])],
        "_orphanedCollections" : []})

db.createGraph(name=MyGraph, createCollections=False)