After needing python to work faster for my day job, in startup that I work for we use Python on OpenWrt... and finally found the solution!
To compile all python modules into pyc issue this command:
python -m compileall
Make sure you have at least 7MB of internal storage space!
Now my python scripts start under 1.5 seconds and previously it would take them 6-8 seconds!
If you have additional python modules installed you need to compile them also, so for me I needed to additionally run these commands:
python -m compileall /usr/lib/python2.7/site-packages/serial/*.py
python -m compileall /usr/lib/python2.7/site-packages/serial/tools/*.py
python -m compileall /usr/lib/python2.7/site-packages/serial/urlhandler/*.py