reaction is incorrectly added

[jotech]

I have noticed some strange behaviour when adding a reaction that
contains the same metabolite on both sides:

from cobra import Model, Reaction, Metabolite

model = Model("test")

A = Metabolite("A", formula="C1", name="Substance A", compartment="c")
B = Metabolite("B", formula="C2", name="Substance B", compartment="c")
C = Metabolite("C", formula="C3", name="Substance C", compartment="c")

reaction = Reaction("new_reaction")
reaction.name = "Test reaction"

reaction.add_metabolites({A: -1.0,
                          B: -1.0,
                          A: 1.0,
                          C: 1.0})

print reaction.reaction
model.add_reaction(reaction)

output is

B --> C + A

instead of

A + B --> C + A

I'm working with cobra 0.3.0.dev.

[aebrahim]

A python dict requires unique keys. If you include A twice in the dict as you define it, it will only keep the second definition.

>>> {"a": -1, "a": 1}
{'a': 1}

So cobrapy is handling what it is being given correctly.