__init__.py 文件源码

def _which(self, program):
        """Simple function to determine the path of an executable.

        Borrowed from https://github.com/amoffat/sh/blob/master/sh.py#L300.
        Thanks Andrew Moffat! sh is pretty awesome :^)
        """
        def is_exe(fpath):
            return (os.path.exists(fpath) and
                    os.access(fpath, os.X_OK) and
                    os.path.isfile(os.path.realpath(fpath)))

        fpath, fname = os.path.split(program)
        if fpath:
            if is_exe(program):
                return program
        else:
            if "PATH" not in os.environ:
                return None
            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