.. py:currentmodule:: tulip 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 :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: * :class:`tlp.BooleanProperty` : associate boolean values to nodes and edges * :class:`tlp.ColorProperty` : associate colors (r,g,b,a) to nodes and edges * :class:`tlp.DoubleProperty`: associate floating point values to nodes and edges * :class:`tlp.IntegerProperty`: associate integer values to nodes and edges * :class:`tlp.LayoutProperty`: associate positions (x,y,z) to nodes and bends/control points to edges * :class:`tlp.SizeProperty`: associate sizes (width,height,depth) to nodes and edges * :class:`tlp.StringProperty`: associate string values to nodes and edges Lists of values can also be associated to graph elements through the use of the vector property classes listed below : * :class:`tlp.BooleanVectorProperty` : associate lists of boolean values to nodes and edges * :class:`tlp.ColorVectorProperty` : associate lists of colors (r,g,b,a) to nodes and edges * :class:`tlp.DoubleVectorProperty`: associate lists of floating point values to nodes and edges * :class:`tlp.IntegerVectorProperty`: associate lists of integer values to nodes and edges * :class:`tlp.CoordVectorProperty`: associate lists of positions (x,y,z) to nodes and to edges * :class:`tlp.SizeVectorProperty`: associate lists of sizes (width,height,depth) to nodes and edges * :class:`tlp.StringVectorProperty`: associate lists of string values to nodes and edges In Tulip, there is two different kinds of graph properties : * **Local property** : means that the property belongs to the graph. Its ancestors in the sub-graph hierarchy do not have access to it but its descendants do. * **Inherited property** : means that the property is inherited from an ancestor in the sub-graph 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 :class:`tlp.Graph` class like :meth:`tlp.Graph.getDoubleProperty`, :meth:`tlp.Graph.getLayoutProperty`, :meth:`tlp.Graph.getIntegerVectorProperty`, ... (see :ref:`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 graph.delLocalProperty("myMetric") # Anonymous properties can also be instantiated the following way myOtherMetric = tlp.DoubleProperty(graph) 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) == graph.target(e)) # the syntax below can also be used # loop[e] = (graph.source(e) == graph.target(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"