[ase-users] Weird behaviour in "Parameters" class defined in calculator.py

[Joakim Löfgren]

Hi,


While playing around with a custom calculator I encountered some weirdness when dealing with the Parameters class that is defined in calculator.py. The root of my issue seems to be that you can't update a Parameters object with a dictionary where one of the values is another dictionary. To my understanding Parameters is supposed to behave like a regular dict only with some extra features like shorthand access to keys.


Here is a MWE demonstrating the issue:


from ase.calculators.calculator import Parameters
p = Parameters()
p.update({'foo': 1}) # works
p.update({'bar': {'baz': 2}}) # KeyError


The code responsible (with some context) in the update method (line 189) of Parameters is:


for key, value in other:

    if isinstance(value, dict) and isinstance(self[key], dict):
        self[key].update(value)
     else:
         self[key] = value


Here, the 2nd part of the if statement fails unless the key already exists. I think this could be fixed without breaking any of the existing calculators using something along the lines of:


for key, value in other:

    if isinstance(value, dict) and key in self:
        self[key].update(value)
    else:
        self[key] = value

What do you think?

Cheers,
Joakim Löfgren


___________________
Joakim Löfgren
Ph.D. Student
Department of Physics
Division of Materials and Surface Theory
Chalmers University of Technology


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listserv.fysik.dtu.dk/pipermail/ase-users/attachments/20170301/96d2c2f2/attachment.html>