Check if a program exists from a python script [duplicate]

Answer 1

shutil.which

Let me recommend an option that has not been discussed yet: a Python implementation of which, specifically shutil.which. It was introduced in Python 3.3 and is cross-platform, supporting Linux, Mac, and Windows. It is also available in Python 2.x via whichcraft. You can also just rip the code for which right out of whichcraft here and insert it into your program.

def is_tool(name):
    """Check whether `name` is on PATH and marked as executable."""

    # from whichcraft import which
    from shutil import which

    return which(name) is not None

---

distutils.spawn.find_executable

Another option that has already been mentioned is distutils.spawn.find_executable.

find_executable's docstring is as follows:

Tries to find 'executable' in the directories listed in 'path'

So if you pay attention, you'll note that the name of the function is somewhat misleading. Unlike which, find_executable does not actually verify that executable is marked as executable, only that it is on the PATH. So it's entirely possible (however unlikely) that find_executable indicates a program is available when it is not.

For example, suppose you have a file /usr/bin/wget that is not marked executable. Running wget from the shell will result in the following error: bash: /usr/bin/wget: Permission denied. which('wget') is not None will return False, yet find_executable('wget') is not None will return True. You can probably get away with using either function, but this is just something to be aware of with find_executable.

def is_tool(name):
    """Check whether `name` is on PATH."""

    from distutils.spawn import find_executable

    return find_executable(name) is not None

Answer 2

You could use a subprocess call to the binary needed with :

• "which" : *nix
• "where" : Win 2003 and later (Xp has an addon)

to get the executable path (supposing it is in the environment path).

import os 
import platform
import subprocess

cmd = "where" if platform.system() == "Windows" else "which"
try: 
    subprocess.call([cmd, your_executable_to_check_here])
except: 
    print "No executable"

or just use Ned Batchelder's wh.py script, that is a "which" cross platform implementation:

http://nedbatchelder.com/code/utilities/wh_py.html

Answer 3

I'd go for:

import distutils.spawn

def is_tool(name):
  return distutils.spawn.find_executable(name) is not None