In Component.update_reactions parameters are being copied and re-updated in a way I don't understand

[WilliamIX]

Create the parameter values for this reaction

parameters = self.parameters.copy()
parameters.update(self.parameters)

As far as I can tell, this code is incredibly redundant and doesn't do anything.

[murrayrm]

Probably something left over from the way in which the code got created.

The reason to create a copy of the parameters is because Python passes by reference (and so you don't want to overwrite the parameter dictionary that you were passed). But the second line above can be deleted and nothing will change (assuming there were no steps in the middle).