What are the limitations of distributing .pyc files?

Question

I've started working on a commercial application in Python, and I'm weighing my options for how to distribute the application.

Aside from the obvious (distribute sources with an appropriate commercial license), I'm considering distributing just the .pyc files without their corresponding .py sources. But I'm not familiar enough with Python's compatibility guarantees to know if this is even workable, much less whether it's a good idea or not.

Are .pyc files independent of the underlying OS? For example, would a .pyc file generated on a 64-bit Linux machine work on a 32-bit Windows machine?

I've found that .pyc file should be compatible across bugfix releases, but what about major and minor releases? For example, would a file generated with Python 3.1.5 be compatible with Python 3.2.x? Or would a .pyc file generated with Python 2.7.3 be compatible with a Python 3.x release?

Edit:

Primarily, I may have to appease stakeholders who are uncomfortable distributing sources. Distributing .pyc's without sources may give them some level of comfort, since it would require the extra step of decompiling to get at the sources, even if that step is somewhat trivial. Just enough of a barrier to keep honest people honest.

Answer 1

For example, would a file generated with Python 3.1.5 be compatible with Python 3.2.x?

No.

Or would a .pyc file generated with Python 2.7.3 be compatible with a Python 3.x release?

Doubly no.

I'm considering distributing just the .pyc files without their corresponding .py sources.

Python bytecode is high-level and trivially decompilable.

Answer 2

You certainly could distribute the .pyc files only. As Cat mentioned, no it would not be compatible with different major version of Python. It might prevent some people from viewing the source code, but the .pyc files are very easy to decompile. Basically if you can compile it, you can decompile it.

You could use a binary packager like py2exe / py2app / freeze. I've never tried them but someone could still decompile them if they wanted to.

Answer 3

As Cat said, pyc files are not cross version safe. Though what you're trying to hide from the users determines what you need to do.

As for source code, there is no good way to hide Python source code in a distributed application. If you just trying to hide specific details you could pack those into a C extension -- which would be much harder to decompile.

So if you're worried about code use, put a license attached to the code for no-use or translate the sections you don't want stolen to a compiled language. If you just want code to not be obviously Python, you can create a binary executable that wraps the Python code (though doesn't hide the actual details if someone extracts them from the file).