You just simply use it, if specific argument require python 2 sting you simply call bytes() on it. For example old_function(bytes(myarg)) if it needs to be a

You just simply use it, if specific argument require python 2 sting you simply call bytes() on it. For example old_function(bytes(myarg)) if it needs to be a literal: old_function(b"literal") That's what I do, and works for me so far.