FalloffRate.third_body_concentration is not defined

[bryanwweber]

In FalloffRate.falloff_function(), the conc3b parameter can be passed as None, in which case self.third_body_concentration is used. However, FalloffRate.third_body_concentration is not defined in the pyx file, so this raises an attribute error:

import cantera as ct
gas = ct.Solution("gri30.yaml")
r = gas.reaction(11).rate
r.falloff_function(300)

I think we can improve the user experience in this case, either by eliminating the default argument or raising a more useful error message.

cantera/interfaces/cython/cantera/reaction.pyx

Lines 421 to 427 in a394423

	def falloff_function(self, double temperature, conc3b=None):
	"""
	Evaluate the falloff function
	"""
	if conc3b is None:
	conc3b = self.third_body_concentration
	return self.falloff.evalF(temperature, conc3b)