Getting / Setting data on graph elements

Tulip allows to associate different kind of data to the graph elements. These data are stored in a structure called “property” which can be seen as an array indexed by the nodes and edges of a graph. The class tlp.PropertyInterface is the base interface for each graph property object. For each data type that can be attached to graph elements, there is a specific property class. Below is an exhaustive list of these classes:

Lists of values can also be associated to graph elements through the use of the vector property classes listed below :

In Tulip, there is two different kinds of graph properties :

  • Local property : means that the property belongs to the graph. Its ancestors in the subgraph hierarchy do not have access to it but its descendants do.

  • Inherited property : means that the property is inherited from an ancestor in the subgraph hierarchy. Only the graph whose the property is local can delete it.

Creating / Accessing / Deleting a graph property

Before using a graph property, you have to create it. To do so, use specific methods from the tlp.Graph class like tlp.Graph.getDoubleProperty(), tlp.Graph.getLayoutProperty(), tlp.Graph.getIntegerVectorProperty(), … (see Access and compute graph properties). All these methods take a string identifier as parameter to name the property. The created property can then be accessed / deleted through its identifier. It is also possible to create anonymous properties that won’t be managed by a graph. Below is some code samples that illustrate these features:

# create a DoubleProperty called "myMetric" if it does not exist
# otherwise return the already created property
myMetric = graph.getDoubleProperty("myMetric")

# Once created, a property can also be accessed through this syntax
myMetric = graph["myMetric"]

# The property can be deleted by the graph that has created it

# Anonymous properties can also be instantiated the following way;
# they will be deleted by the Python garbage collector, when needed.
myOtherMetric = graph.doubleProperty()

Working with graph properties

The sample code below illustrate how to set / get data on graph elements through the use of a graph property:

# creating an integer property called "degree"
degree = graph.getIntegerProperty("degree")

# creating a Boolean property called "loop"
loop = graph.getBooleanProperty("loop")

# filling the properties
for n in graph.getNodes():
  degree.setNodeValue(n, graph.deg(n))
  # the syntax below can also be used
  # degree[n] = graph.deg(n)

for e in graph.getEdges():
  loop.setEdgeValue(e, graph.source(e) ==
  # the syntax below can also be used
  # loop[e] = (graph.source(e) ==

# reading the properties
for n in graph.getNodes():
  d = degree.getNodeValue(n)
  # the syntax below can also be used
  # d = degree[n]
  print "degree of ", n, " = ", d

for e in graph.getEdges():
  isLoop = loop.getEdgeValue(e)
  # the syntax below can also be used
  # isLoop = loop[e]
  if isLoop:
    print e, " is a loop"