Fix string representation for Bounded distributions

[KoljaBauer]

Description of your problem

I am trying to render a pym3 model as a graph. Calling pymc3.model_to_graphviz(model) with a model that contains Bounded variables (variables with a distribution wrapped by a bounded distribution) leads to an error:

import pymc3

with pymc3.Model(name="test") as model:
        var = pymc3.Bound(pymc3.Normal, lower=1)('test_var', mu=1, sigma=1)
        img = pymc3.model_to_graphviz(model)

Please provide the full traceback.

Traceback (most recent call last):
  File "./replicate_bug.py", line 13, in <module>
    test_graphviz()
  File "./replicate_bug.py", line 9, in test_graphviz
    img = pymc3.model_to_graphviz(model)
  File "/home/new_env/lib/python3.8/site-packages/pymc3/model_graph.py", line 233, in model_to_graphviz
    return ModelGraph(model).make_graph()
  File "/home/new_env/lib/python3.8/site-packages/pymc3/model_graph.py", line 213, in make_graph
    self._make_node(var_name, graph)
  File "/home/new_env/lib/python3.8/site-packages/pymc3/model_graph.py", line 149, in _make_node
    label = str(v).replace(" ~ ", "\n~\n")
  File "/home/new_env/lib/python3.8/site-packages/pymc3/model.py", line 83, in __str__
    return self._str_repr(formatting="plain", **kwargs)
  File "/home/new_env/lib/python3.8/site-packages/pymc3/model.py", line 77, in _str_repr
    return self.distribution._str_repr(name=name, dist=dist, formatting=formatting)
  File "/home/new_env/lib/python3.8/site-packages/pymc3/distributions/distribution.py", line 176, in _str_repr
    param_values = [
  File "/home/new_env/lib/python3.8/site-packages/pymc3/distributions/distribution.py", line 177, in <listcomp>
    get_repr_for_variable(getattr(dist, x), formatting=formatting) for x in param_names
AttributeError: '_ContinuousBounded' object has no attribute 'distribution'

Graphviz was installed by executing the following steps:

git clone https://gitlab.com/graphviz/graphviz.git
cd graphviz
./autogen.sh
./configure
make
make install
cd ..
pip install graphviz

Proposed solution:

In method _str_repr of distribution.py, replace

param_values = [
            get_repr_for_variable(getattr(dist, x), formatting=formatting) for x in param_names
        ]

with

param_values = []
        for x in param_names:
            if hasattr(dist, x):
                if getattr(dist, x) is None:
                    param_values.append("")
                else:
                    param_values.append(get_repr_for_variable(getattr(dist, x), formatting=formatting))
            else:
                param_values.append("")

and additionally:
In method _distr_name_for_repr of distribution.py, add:

#If the distribution is Bounded, print the wrapped distribution
if(self.__class__.__name__ == "_ContinuousBounded"):
    return "Bound " + self._wrapped.__class__.__name__

Versions and main components

• PyMC3 Version: 3.9.3
• Theano Version: Theano-PyMC==1.0.10
• Python Version: Python 3.8.6
• Operating system: Fedora
• How did you install PyMC3: pip install git+https://github.com/pymc-devs/pymc3

[twiecki]

Thanks for the report and proposed fix @KoljaBauer, want to do a PR?

[AlexAndorra]

As Thomas said, thanks for reporting and proposing a fix @KoljaBauer !
I'm also pinging @Spaak here, as he did a pretty in-depth PR about str representations recently

[Spaak]

I third the thanks for the report and proposing a fix @KoljaBauer! :)

As for the fix, I think it's probably better to fix this at the level of _Bounded (overriding), rather than change the generic parent code in Distribution to account for this special case. (I'd be happy to fix it, or let me know if you want to have a go at it yourself @KoljaBauer).

[KoljaBauer]

@Spaak Thank you for addressing it so quick!