I have a python server that forks itself once it receives a request.  The python service has several C++ .so objects it can call into, as well as the python process itself.  
My question is, in any one of these processes, I would like to be able to see how much CPU all instances of this server are currently using.  So lets say I have foo.py, I want to see how much CPU all instances of foo.py are currently using.  For example, foo.py(1) is using 200% cpu, foo.py(2) is using 300%, and foo.py(3) is using 50%, id like to arrive at 550%.  
The only way I can think of doing this myself is getting the PID of every process and scanning through the /proc filesystem.  Is there a more general way available within C/Python/POSIX for such an operation?  
Thank you!
Here is the only way to do that I can think. It is a bit confusing but if you follow the steps it is very simple:

If I want to select total cpu use of Google Chrome process:
$ps -e -o pcpu,comm | grep chrome | awk '{ print $1 }' | paste -sd+ |
  bc -l
Query total CPU usage of all instances of a process on Linux OS