def __new__(self,graph,source=None,target=None,key=None,eh=None):
# edge handle given, reconstruct node object
if eh is not None:
(source,target)=(gv.agtail(eh),gv.aghead(eh))
s=Node(graph,nh=source)
t=Node(graph,nh=target)
# no edge handle, search for edge and construct object
else:
s=Node(graph,source)
t=Node(graph,target)
try:
eh=gv.agedge(graph.handle,
s.handle,
t.handle,
key,
_Action.find)
except KeyError:
raise KeyError("Edge %s-%s not in graph."%(source,target))
tp=tuple.__new__(self,(s,t))
tp.ghandle=graph.handle
tp.handle=eh
tp.attr=ItemAttribute(eh,3)
tp.key=key
return tp
def add_edge(self,u,v=None,key=None,**attr):
"""Add a single edge between nodes u and v.
If the nodes u and v are not in the graph they will added.
If u and v are not strings, conversion to a string will be attempted.
String conversion will work if u and v have valid string representation
(try str(u) if you are unsure).
>>> G=AGraph()
>>> G.add_edge('a','b')
>>> G.edges()
[('a', 'b')]
The optional key argument allows assignment of a key to the
edge. This is especially useful to distinguish between
parallel edges in multi-edge graphs (strict=False).
>>> G=AGraph(strict=False)
>>> G.add_edge('a','b','first')
>>> G.add_edge('a','b','second')
>>> sorted(G.edges())
[('a', 'b', 'first'), ('a', 'b', 'second')]
Attributes can be added when edges are created
>>> G.add_edge('a','b',color='green')
Attributes must be valid strings.
See http://www.graphviz.org/doc/info/attrs.html
for a list of attributes.
"""
if v is None: (u,v)=u # no v given, assume u is an edge tuple
try:
uh=Node(self,u).handle
except:
self.add_node(u)
uh=Node(self,u).handle
try:
vh=Node(self,v).handle
except:
self.add_node(v)
vh=Node(self,v).handle
try:
if key is not None:
if not self._is_string_like(key): key=str(key)
eh=gv.agedge(self.handle,uh,vh,key,_Action.create)
e=Edge(self,eh=eh)
e.attr.update(**attr)
except KeyError:
return None # silent failure for strict graph, already added
