The force-option from compileall seems not to rebuild the bytecode files if they already exist. Here is an example of 2 calls:
root@ubuntu:~# python3 -m compileall -f
Skipping current directory
Listing '/usr/lib/python3.3'...
Compiling '/usr/lib/python3.3/__phello__.foo.py'...
Compiling '/usr/lib/python3.3/_compat_pickle.py'...
Compiling '/usr/lib/python3.3/_dummy_thread.py'...
...
Compiling '/usr/lib/python3.3/webbrowser.py'...
Compiling '/usr/lib/python3.3/xdrlib.py'...
Compiling '/usr/lib/python3.3/zipfile.py'...
Listing '/usr/lib/python3.3/plat-x86_64-linux-gnu'...
Listing '/usr/lib/python3.3/lib-dynload'...
Listing '/usr/local/lib/python3.3/dist-packages'...
Listing '/usr/lib/python3/dist-packages'...
root@ubuntu:~# python3 -m compileall -f
Skipping current directory
Listing '/usr/lib/python3.3'...
Listing '/usr/lib/python3.3/plat-x86_64-linux-gnu'...
Listing '/usr/lib/python3.3/lib-dynload'...
Listing '/usr/local/lib/python3.3/dist-packages'...
Listing '/usr/lib/python3/dist-packages'... |