Process name 'masked' by /usr/bin/python and /bin/su

I'm trying to use the pidof command to see my script is already running as I only want this executable if the script is not already running, however, it seems the pidof command is not returning the *pid* of the script using the name which is displayed in ps -ef output. Instead it is masking this name as either /usr/bin/python or /bin/su. Can someone shed some light on what is going on and how I can run pidof 'script.py -v' to see if the script is running or not? [root@cloud proc]# pidof python /some/dir/script.py -v > pidof: invalid options on command line! [root@cloud proc]# pidof "python /some/dir/script.py -v" > [root@cloud proc]# pidof "su - user -c python /some/dir/script.py -v" > [root@cloud proc]# ps -ef | grep script.py > root 5409 31739 0 13:07 pts/1 00:00:00 su - user -c python /some/dir/script.py -v > user 5414 5409 96 13:07 ? 01:00:40 python /some/dir/script.py -v [root@cloud proc]# ls -l /proc/5409/exe > lrwxrwxrwx. 1 root root 0 Oct 13 14:04 /proc/5409/exe -> /bin/su [root@cloud proc]# ls -l /proc/5414/exe > lrwxrwxrwx. 1 user user 0 Oct 13 14:04 /proc/5414/exe -> /usr/bin/python [root@cloud proc]# pidof /bin/su > 31715 6308 5409 [root@cloud proc]# pidof /usr/bin/python > 5414