I think there is one more method to protect your Python code; part of the Obfuscation method. I beleive there was a game like Mount and Blade or something that changed and recompiled their own python interpreter (the original interpreter which i believe is open source) and just changed the OP codes in the OP code table to be different then the standard python OP codes.
So the python source is unmodified but the file extentions of the pyc files are different and the op codes don't match to the public python.exe interpreter. If you checked the games data files all the data was in Python source format.
All sorts of nasty tricks can be done to mess with amature hackers this way. Stopping a bunch of noob hackers is easy. It's the pro hackers that you will not likely beat. But most companies don't keep pro hackers on staff long I imagine (likely because things get hacked). But amature hackers are all over the place (read as curious IT staff).
You could for example, in a modified interpreter, allow it to check for certain comments or docstrings in your source. You could have special OP codes for such lines of code. For example:
OP 234 is for source line "# Copyright I wrote this"
or compile that line into op codes that are equivelent to "if False:" if "# Copyright" is missing. Basically disabling a whole block of code for what appears to be some obsure reason.
One use case where recompiling a modified interpreter may be feasable is where you didn't write the app, the app is big, but you are paid to protect it, such as when you're a dedicated server admin for a financial app.
I find it a little contradictory to leave the source or opcodes open for eyeballs, but use SSL for network traffic. SSL is not 100% safe either. But it's used to stop MOST eyes from reading it. A wee bit precaution is sensible.
Also, if enough people deem that Python source and opcodes are too visible, it's likely someone will eventually develope at least a simple protection tool for it. So the more people asking "how to protect Python app" only promotes that development.