Why hash of pymatgen.analysis.reaction_calculator.BalancedReaction is hardcoded as int 7?

[DanielYang59]

I noticed the following definition while working with BalancedReaction, just wondering why this magic number 7?

pymatgen/pymatgen/analysis/reaction_calculator.py

Lines 173 to 174 in a5a4887

	def __hash__(self) -> int:
	return 7

This would make BalancedReaction "hashable", but then all instances would have the same hash?

[janosh]

beats me. i assume there's no good reason for this particular value. we could probably change it to

 def __hash__(self) -> int: 
    return hash((self.reactants_coeffs, self.products_coeffs))

or remove it altogether

[DanielYang59]

That makes sense. But I guess it might be better to provide a hash in case someone need it for some reason.

With that said, maybe hash((self.coeffs, self.reactants, self.products)) to take into account not only coefficients but species themselves? I could try to implement this change if so.
Sorry I thought reactants_coeffs is just the coefficients, you are right.

[janosh]

I could try to implement this change if so.

go ahead! also, maybe add a comment that the need for a hash method is unclear (unless @mkhorton @shyuep know why?)