there are open source projects that decompile them to runnable code, the original symbol names are even intact - this means you don't lose the original naming of variables, functions, arguments, etc.
They're fairly reversable out of the box. There are some modifications to cx-freeze which allow you to bundle your code in a way that makes it more difficult to reverse. What are you shipping that you need source code security with?
there are open source projects that decompile them to runnable code, the original symbol names are even intact - this means you don't lose the original naming of variables, functions, arguments, etc.