Mistake in regex string of ion_or_solid_comp_object leads to example string formula "Na[+]" failing

[IsaacGentle]

Python version

Python 3.12.3

Pymatgen version

2024.11.13

Operating system version

Windows 10

Current behavior

The following code leads to an error (ValueError: + is an invalid formula!)

from pymatgen.analysis.pourbaix_diagram import ion_or_solid_comp_object
fails = ion_or_solid_comp_object('Na[+]')

Even though the definition of ion_or_solid_comp_object states that the argument string should be formatted as 'Na[+]'

def ion_or_solid_comp_object(formula):
    """Get an Ion or Composition object given a formula.

    Args:
        formula: String formula. Eg. of ion: NaOH(aq), Na[+];
            Eg. of solid: Fe2O3(s), Fe(s), Na2O

    Returns:
        Composition/Ion object
    """
    if re.match(r"\[([^\[\]]+)\]|\(aq\)", formula):
        comp_obj = Ion.from_formula(formula)
    elif re.search(r"\(s\)", formula):
        comp_obj = Composition(formula[:-3])
    else:
        comp_obj = Composition(formula)
    return comp_obj

In it's current form, the string needs to be '[+]Na' in order for it to work:

from pymatgen.analysis.pourbaix_diagram import ion_or_solid_comp_object
works = ion_or_solid_comp_object('[+]Na')

Expected Behavior

If 'Na[+]' is the desired string format, the definition of ion_or_solid_comp_object should be modified

L398 of pourbaix_diagram.py is currently:

if re.match(r"\[([^\[\]]+)\]|\(aq\)", formula):

https://github.com/materialsproject/pymatgen/blob/da607e86f9ce8aec942067c6c1a4fda6e04915dd/src/pymatgen/analysis/pourbaix_diagram.py#L398C18-L398C19

I suggest replacement with

if re.match(r".*\[([^\[\]]+)\]|\(aq\)", formula):

I am not super familiar with git workflows and pull requests so I have sent this as an issue. Please advise if you think this is something that should be fixed and if you wish me to do a pull request :)

Minimal example

from pymatgen.analysis.pourbaix_diagram import ion_or_solid_comp_object

works = ion_or_solid_comp_object('[+]Na')
fails = ion_or_solid_comp_object('Na[+]')

Relevant files to reproduce this bug

No response

[DanielYang59]

Hi @IsaacGentle thanks for reporting and I could confirm this issue. For a quick guide on making contributions to a project, you could checkout the guide here.

I could confirm your fix indeed work, but things looks more complex that this as some other formulas still don't work (for example Cl[-]).

Also the unit test for this helper method seems missing, so I might take over from here and fix this :) Thanks again for reporting and investigating.

---

A small tip, to share a code block, you could use the permalink instead of copying the code block.

Another small tip, to show differences in code, you could add diff, which would look like:

- if re.match(r"\[([^\[\]]+)\]|\(aq\)", formula):
+ if re.match(r".*\[([^\[\]]+)\]|\(aq\)", formula):

---

Update: looks like ion_or_solid_comp_object is not used across the code base at all, not sure about its use case, and it looks like a private helper method to me

[IsaacGentle]

Hi @DanielYang59, thanks a lot for your comprehensive reply and helpful tips! Interesting that ion_or_solid_comp_object is not used across the code base. To add extra information about how I discovered this minor bug, I was use the pymatgen scripts to generate Pourbaix diagrams, but I was manually adding some of the ionic species using ion_or_solid_comp_object.

[DanielYang59]

No problem at all. Thanks for sharing the context (though it still looks more like a private function to me, but I wouldn't rename it to private for now as I'm not super familiar with pourbaix_diagram module)

Happy coding in the new year!