Question

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)

Answer 1

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.