import tarfile, os

def extract_tar(file_path, dest_dir = "."):
    print('Extracting "{:s}" to "{:s}"'.format(file_path, dest_dir))
    with tarfile.open(file_path) as tar:
        tar.extractall(dest_dir)
        tar.close()

def which(program, additional_paths = None):

    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:
        paths = os.environ["PATH"].split(os.pathsep);
        if additional_paths != None:
            paths.append(additional_paths)
        for path in paths:
            path = path.strip('"')
            exe_file = os.path.join(path, program)
            if is_exe(exe_file):
                return exe_file

    return None