raspberry pi access point status

I don't know if there is a library function to check if there is an access point created or not. But on the command line you can use iw or wpa_cli. iw is more generic, with wpa_cli you have to specify the interface name, but you can get more details if needed.

rpi ~$ iw dev | grep 'type AP'
        type AP

# or just check for the return code:
rpi ~$ iw dev | grep --quiet 'type AP'
rpi ~$ echo $?
0

rpi ~$ wpa_cli -iwlan0 status | grep 'mode=AP'
mode=AP

# or just check for the return code:
rpi ~$ wpa_cli -iwlan0 status | grep --quiet 'mode=AP'
rpi ~$ echo $?
0