Graphviz - AttributeError: object has no attribute 'partition'

Question

I'm using graphviz with my Django models to render graphs from the following python script for each automata:

alphabets = automata.alphabet_set.all()
states = automata.states_set.all()
transitions = automata.transition_set.all()
dot = gv.Graph()
for state in states:
    dot.node(state.state, state.state)
for transition in transitions:
    dot.edge(transition.current_state, transition.next_state, transition.input)
dot.render( automata.id + '.gv', view=True)

And these are my models:

class Automata(models.Model):
    pass

class Alphabet(models.Model):
    alphabet = models.CharField()
    automata = models.ForeignKey(Automata, on_delete = models.CASCADE)

class States(models.Model):
    state = models.CharField()
    automata = models.ForeignKey(Automata, on_delete = models.CASCADE)

class Transition(models.Model):
    current_state = models.ForeignKey(States, on_delete = models.CASCADE, related_name = 'current')
    input = models.ForeignKey(Alphabet, on_delete = models.CASCADE)
    next_state = models.ForeignKey(States, on_delete = models.CASCADE, related_name = 'next')
    automata = models.ForeignKey(Automata, on_delete = models.CASCADE)

but everytime I try to execute my script I get the following error:

Traceback (most recent call last):
  File "make_graph.py", line 36, in <module>
    dot.edge(transition.current_state, transition.next_state, transition.input)
  File "/home/nids/automata/auto/lib/python3.5/site-packages/graphviz/dot.py", line 116, in edge
    tail_name = self.quote_edge(tail_name)
  File "/home/nids/automata/auto/lib/python3.5/site-packages/graphviz/lang.py", line 63, in quote_edge
    node, _, rest = identifier.partition(':')
AttributeError: 'States' object has no attribute 'partition'

Knowing that I have no error if I simply do: dot.edge('A', 'B', 'edge label')

Answer 1

The graphvis code is expecting a string to be passed into it, not a States object (your model).

You can see this in the source code in the quote_edge function.