After a page of sympy manipulations I get and expression involving LambertW, but the answer given is for the zeroth branch cut. I can tell that I wanted the -1 branch. So, I’d like to change every occurrence of LambertW(y) into LambertW(y, -1).real, where y is an arbitrary sympy expression (that is different in each instance), in a set of expressions that are large enough so that doing it by hand is error prone.

There must be an easy way.