erste Dateien in Graphen

Graphen/shortest_path_visualisation.py

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+"""
+.. _tutorials-shortest-paths:
+
+==============
+Shortest Paths
+==============
+
+This example demonstrates how to find the shortest distance between two vertices
+of a weighted or an unweighted graph.
+"""
+import igraph as ig
+import matplotlib.pyplot as plt
+
+# %%
+# To find the shortest path or distance between two nodes, we can use :meth:`igraph.GraphBase.get_shortest_paths`. If we're only interested in counting the unweighted distance, then we can do the following:
+g = ig.Graph(
+    6,
+    [(0, 1), (0, 2), (1, 3), (2, 3), (2, 4), (3, 5), (4, 5)]
+)
+results = g.get_shortest_paths(1, to=4, output="vpath")
+
+# results = [[1, 0, 2, 4]]
+
+# %%
+# We can print the result of the computation:
+if len(results[0]) > 0:
+    # The distance is the number of vertices in the shortest path minus one.
+    print("Shortest distance is: ", len(results[0])-1)
+else:
+    print("End node could not be reached!")
+
+# %%
+# If the edges have weights, things are a little different. First, let's add
+# weights to our graph edges:
+g.es["weight"] = [2, 1, 5, 4, 7, 3, 2]
+
+# %%
+# To get the shortest paths on a weighted graph, we pass the weights as an
+# argument. For a change, we choose the output format as ``"epath"`` to
+# receive the path as an edge list, which can be used to calculate the length
+# of the path.
+results = g.get_shortest_paths(0, to=5, weights=g.es["weight"], output="epath")
+
+# results = [[1, 3, 5]]
+
+if len(results[0]) > 0:
+    # Add up the weights across all edges on the shortest path
+    distance = 0
+    for e in results[0]:
+        distance += g.es[e]["weight"]
+    print("Shortest weighted distance is: ", distance)
+else:
+    print("End node could not be reached!")
+
+# %%
+# .. note::
+#
+#     - :meth:`igraph.GraphBase.get_shortest_paths` returns a list of lists becuase the `to` argument can also accept a list of vertex IDs. In that case, the shortest path to all each vertex is found and stored in the results array.
+#     - If you're interested in finding *all* shortest paths, take a look at :meth:`igraph.GraphBase.get_all_shortest_paths`.
+
+# %%
+# In case you are wondering how the visualization figure was done, here's the code:
+g.es['width'] = 0.5
+g.es[results[0]]['width'] = 2.5
+
+fig, ax = plt.subplots()
+ig.plot(
+    g,
+    target=ax,
+    layout='circle',
+    vertex_color='steelblue',
+    vertex_label=range(g.vcount()),
+    edge_width=g.es['width'],
+    edge_label=g.es["weight"],
+    edge_color='#666',
+    edge_align_label=True,
+    edge_background='white'
+)
+plt.show()

Graphen/simplegraph.py

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+list_of_nodes = list()
+list_of_edges = list()
+
+class node:
+    def __init__(self, name=""):
+         self.name = name
+         
+    def get_name(self):
+        return self.name
+    
+    def set_name(self, new_name=""):
+        if new_name != self.name:
+            old_name = self.name
+            self.name = new_name
+            print("name of node {} changed to {}".format(old_name, new_name))
+        else:
+            pass
+         
+n1 = node("A")
+n2 = node("B")
+n3 = node("C")
+
+for n in [n1,n2,n3]:
+    list_of_nodes.append(n)
+
+print(list_of_nodes)
+
+for n in list_of_nodes:
+    print(n.get_name())
+
+list_of_node_names = [x.get_name() for x in list_of_nodes]
+
+print(list_of_node_names)
+
+
+class edge:
+    def __init__(self, nstart, nend):
+        self.nstart = nstart
+        self.nend = nend
+    
+    def __str__(self):
+        s = self.nstart.get_name()
+        e = self.nend.get_name()
+        return "{} -> {}".format(s,e)
+
+e1 = edge(n1, n2)
+print(e1)