compared to invoking a python library function that does the same thing. 
I've some legacy code that uses Popen to invoke a executable with some parameters. 
Now there a python library that supports that same function. 
I was wondering what the performance implications are.
Forking a separate process to do something is almost always much more expensive than calling a function that does the same thing. But if that Python function is very inefficient, and the OS forks new processes quickly (i.e., is a UNIX variant,) you could imagine a rare case where this is not true -- but it will definitely be rare.
What is the performance overhead of Popen in python