I am trying to write a cross-platform python program that would run in the background, monitor all keyboard events and when it sees some specific shortcuts, it generates one
There is no such API. My solution was to write a helper module which would use a different helper depending on the value of os.name.
On Windows, use the Win32 extensions.
On Linux, things are a bit more complex since real OSes protect their users against keyloggers[*]. So here, you will need a root process which watches one of[] the handles in /dev/input/. Your best bet is probably looking for an entry below /dev/input/by-path/ which contains the strings "kbd" or "keyboard". That should work in most cases.
[*]: Jeez, not even my virus/trojan scanner will complain when I start a Python program which hooks into the keyboard events...