_environ.py 文件源码

def __setitem__(self, key, value):
        key = _norm_key(path2fsn(key))
        value = path2fsn(value)

        if is_win and PY2:
            # this calls putenv, so do it first and replace later
            try:
                os.environ[_fsn2legacy(key)] = _fsn2legacy(value)
            except OSError:
                raise ValueError

            try:
                set_windows_env_var(key, value)
            except WindowsError:
                # py3+win fails for invalid keys. try to do the same
                raise ValueError
        try:
            self._env[key] = value
        except OSError:
            raise ValueError