In Python, is there a portable and simple way to test if an executable program exists?
By simple I mean something like the which command which would be just perfect. I don't want to search PATH manually or something involving trying to execute it with Popen & al and see if it fails (that's what I'm doing now, but imagine it's launchmissiles)
So basically you want to find a file in mounted filesystem (not necessarily in PATH directories only) and check if it is executable. This translates to following plan: 

enumerate all files in locally mounted filesystems
match results with name pattern
for each file found check if it is executable

I'd say, doing this in a portable way will require lots of computing power and time. Is it really what you need?
Test if executable exists in Python?