Allow multiple branches between buses; remove objects; import SciGRID…

… example

Multiple branches between buses are allowed via nx.MultiGraph; the
branch object is the key for the edge.

Objects can now be gracefully removed.

A network.topology_determined switch indicates whether the topology
has already been calculated / needs to be recalculated.

An example of importing SciGRID is included.

Changes to be committed:
	modified:   .gitignore
	modified:   components.py
	modified:   descriptors.py
	new file:   examples/scigrid-151109/LICENSE
	new file:   examples/scigrid-151109/NOTICE
	new file:   examples/scigrid-151109/import_scigrid.py
	new file:   examples/scigrid-151109/links_de_power_151109.csvdata
	new file:   examples/scigrid-151109/vertices_de_power_151109.csvdata
	new file:   examples/scigrid-151109/vertices_ref_id.csvdata
	new file:   guidelines.org
	modified:   io.py
	modified:   opf.py
	modified:   pf.py

.gitignore

@@ -6,10 +6,10 @@
 
 *.log
 
-*.org
-
 old/
 
 *.ipynb
 
-test/.cache/
+test/.cache/
+
+.~*

components.py

@@ -39,7 +39,7 @@
 from collections import OrderedDict
 from itertools import chain
 
-from .descriptors import Float, String, OrderedDictDesc, Series, GraphDesc
+from .descriptors import Float, String, OrderedDictDesc, Series, GraphDesc, OrderedGraph
 
 from io import export_to_csv_folder, import_from_csv_folder, import_from_pypower_ppc
 
@@ -81,10 +81,10 @@ class Bus(Common):
 
  list_name = "buses"
 
- v_nom = Float()
+ v_nom = Float(default=1.)
  control = String(default="PQ",restricted=["PQ","PV","Slack"])
 
- #2-d location data (e.g. longitude and latitude)
+ #2-d location data (e.g. longitude and latitude; Spatial Reference System Identifier (SRID) set in network.srid)
  x = Float()
  y = Float()
 
@@ -309,8 +309,17 @@ class Network(Basic):
  #limit of total co2-tonnes-equivalent emissions for period
  co2_limit = None
 
+
+ #Spatial Reference System Identifier (SRID) for x,y - defaults to longitude and latitude
+ srid = Float(4326)
+
  graph = GraphDesc()
 
+
+ #booleans for triggering recalculation
+ topology_determined = False
+
+
  def __init__(self, csv_folder_name=None, **kwargs):
 
  #hack so that Series descriptor works when looking for obj.network.snapshots
@@ -347,6 +356,12 @@ def add(self,class_name,name,**kwargs):
  print(class_name,"not found")
  return None
 
+ obj_list = getattr(self,cls.list_name)
+
+ if str(name) in obj_list:
+ print("Failed to add",name,"because there is already an object with this name in",cls.list_name)
+ return
+
  obj = cls(self)
 
  obj.name = name
@@ -355,7 +370,7 @@ def add(self,class_name,name,**kwargs):
  setattr(obj,key,value)
 
  #add to list in network object
- getattr(self,cls.list_name)[obj.name] = obj
+ obj_list[obj.name] = obj
 
  #build branches list
  if isinstance(obj, Branch):
@@ -374,10 +389,33 @@ def add_from(self,object_list):
  def remove(self,obj):
  """Remove object from network."""
 
+ obj_list = getattr(self,obj.__class__.list_name)
+
+ if obj.name not in obj_list:
+ print("Object",obj,"no longer in",obj.__class__.list_name)
+ return
+
+ obj_list.pop(obj.name)
+
+ if isinstance(obj, Branch):
+ self.branches.pop(obj.name)
+
+ if hasattr(obj,"bus"):
+ getattr(obj.bus,obj.__class__.list_name).pop(obj.name)
+
+ del obj
+
+ self.topology_determined = False
+
+
  def build_graph(self):
  """Build networkx graph."""
 
- self.graph.add_edges_from((branch.bus0, branch.bus1, {"obj" : branch}) for branch in self.branches.itervalues())
+ #reset the graph
+ self.graph = OrderedGraph()
+
+ #Multigraph uses object itself as key
+ self.graph.add_edges_from((branch.bus0, branch.bus1, branch, {}) for branch in self.branches.itervalues())
 
 
  def determine_network_topology(self):
@@ -388,20 +426,25 @@ def determine_network_topology(self):
 
  graph = self.graph.__class__(self.graph)
 
- graph.remove_edges_from((branch.bus0,branch.bus1)
+ graph.remove_edges_from((branch.bus0, branch.bus1, branch)
  for branch in chain(self.converters.itervalues(),
  self.transport_links.itervalues()))
 
 
  #now build connected graphs of same type AC/DC
  sub_graphs = nx.connected_component_subgraphs(graph, copy=False)
 
+
+ #remove all old sub_networks
+ for sub_network in list(self.sub_networks.values()):
+ self.remove(sub_network)
+
  for i, sub_graph in enumerate(sub_graphs):
  #name using i for now
  sub_network = self.add("SubNetwork", i, graph=sub_graph)
 
  sub_network.buses.update((n.name, n) for n in sub_graph.nodes())
- sub_network.branches.update((branch.name, branch) for (u, v, branch) in sub_graph.edges_iter(data="obj"))
+ sub_network.branches.update((branch.name, branch) for (u, v, branch) in sub_graph.edges_iter(keys=True))
 
  for bus in sub_network.buses.itervalues():
  bus.sub_network = sub_network
@@ -410,6 +453,9 @@ def determine_network_topology(self):
  branch.sub_network = sub_network
 
 
+ self.topology_determined = True
+
+
 
 class SubNetwork(Common):
  """Connected network of same current type (AC or DC)."""

descriptors.py

@@ -51,7 +51,7 @@
 
 
 
-class OrderedGraph(nx.Graph):
+class OrderedGraph(nx.MultiGraph):
  node_dict_factory = OrderedDict
  adjlist_dict_factory = OrderedDict
 
@@ -109,8 +109,8 @@ def __get__(self,obj,cls):
  return graph
 
  def __set__(self,obj,val):
- if not isinstance(val, nx.Graph):
- raise AttributeError("val must be an nx.Graph")
+ if not isinstance(val, OrderedGraph):
+ raise AttributeError("val must be an OrderedGraph")
  else:
  self.values[obj] = val