...
Downloading BrightSign Python-Only Builds
To download a BrightSign OS BrightSignOS and the Python production build that can be used with your Series 4 player, see BrightSign Python-Only Builds (DOCS-877).
Series 2 and 3 players are not compatible with Python, but Series 5 players and operating systems will be compatible with Python in the near future.
...
The base OS version and the Python-only version should be kept in sync. To install:
Copy the BrightSign OS BrightSignOS to the root of the SD card, then reboot your player.
Copy the Python update to the root of the SD card, then reboot your player.
...