FAQ: Graphs: Python - Building the Graph I

This community-built FAQ covers the “Building the Graph I” exercise from the lesson “Graphs: Python”.

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This exercise can be found in the following Codecademy content:

Computer Science

Complex Data Structures

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After completion of task #4, my code is returning:

{‘Grand Central Station’: <vertex.Vertex object at 0x7feef4ea6710>}

instead of:

{“Grand Central Station”: grand_central}

Any idea how to display the variable name as the value? Thanks!


I highly suspect that it’s because our variable is a Vertex class which doesn’t have a string method?
I think the best way to get that result is by declaring __repr__ method inside Vertex class.
But I still don’t know how to convert the variable name into string as well.
hope someone can explain it better.

I managed to print the variable name to the list. the way I did it was to copy the Vertex.py code to the graph.py code and add the following repr to the vertex class.

  def __repr__(self):
      d = [k for k,v in globals().items() if v is self]    
      return str(d[0])

maybe you can do it somehow differently, but i don’t know how to debug that properly. Would love to know tho! The class is probably not part of globals because it’s in a different file. Therefore, adding the code above to vertex.py would return an index error as the variable d is empty.
here is the complete code:

class Vertex:
  def __init__(self, value):
    self.value = value
    self.edges = {}

  def add_edge(self, vertex):
    self.edges[vertex] = True

  def get_edges(self):
    return list(self.edges.keys())

  def __repr__(self):
      d = [k for k,v in globals().items() if v is self]    
      return str(d[0])

class Graph:
  def __init__(self,directed = False):
    self.directed = directed
    self.graph_dict = {}
  def add_vertex(self,vertex):
    print("Adding "+ vertex.value)
    self.graph_dict[vertex.value] = vertex

grand_central = Vertex("Grand Central Station")

# Uncomment this code after you've defined Graph
railway = Graph()

# Uncomment these lines after you've completed .add_vertex()
1 Like

I managed to get the string value by adding :

def __repr__(self):
  return self.value

in vertex.py


Thank you for this <3