["python","path"]
Test if executable exists in Python?

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)
Easiest way I can think of: def which(program): import os def is_exe(fpath): return os.path.isfile(fpath) and os.access(fpath, os.X_OK) fpath, fname = os.path.split(program) if fpath: if is_exe(program): return program else: for path in os.environ.get("PATH", "").split(os.pathsep): exe_file = os.path.join(path, program) if is_exe(exe_file): return exe_file return None Edit: Updated code sample to include logic for handling case where provided argument is already a full path to the executable, i.e. "which /bin/ls". This mimics the behavior of the UNIX 'which' command. Edit: Updated to use os.path.isfile() instead of os.path.exists() per comments. Edit: path.strip('"') seems like the wrong thing to do here. Neither Windows nor POSIX appear to encourage quoted PATH items.