def _parse_reaction(line, all_species, parameters, reactions, tables):
line_split_arrow = line.split('=>')
if len(line_split_arrow) != 2:
raise InvalidLine(
f"Syntax error on line '{line}': There can only be one reaction per line. In a reaction, "
f"the reactants and products are separated by the arrow '=>'.")
left_side = line_split_arrow[0]
line_split_excl = line_split_arrow[1].split('!')
if len(line_split_excl) != 2:
raise InvalidLine(
f"Syntax error on line '{line}': Each reaction must have its rate specified. The rate "
f"specification goes after the single exclamation mark '!'. The exclamation mark '!' "
f"must not be used elsewhere.")
right_side = line_split_excl[0]
rate_spec = line_split_excl[1]
reaction = Reaction(_parse_species(left_side, all_species),
_parse_species(right_side, all_species))
_parse_rate(reaction, rate_spec, tables,
parameters) # fills attributes rate_fun and table_name
reaction.scale(
parameters) # # scale the rate function: using the 'ratio' parameter
reactions.append(reaction)
