def which(program):
    def is_exe(fpath):
        return os.path.exists(fpath) and os.access(fpath, os.X_OK)

    fpath, _ = os.path.split(program)
    if fpath:
        if is_exe(program):
            return program
    else:
        for path in os.environ['PATH'].split(os.pathsep):
            exe_file = os.path.join(path, program)
            if is_exe(exe_file):
                return exe_file

    return None
Detect whether or not a program is installed.
dataset/ETHPy150Open CGATOxford/cgat/setup.py/which