我目前正在尝试安装一些python软件包，似乎无法弄清楚它为什么不起作用。运行ez_install时出现以下错误：
$ easy_install scipy
error: can't create or remove files in install directory
The following error occurred while trying to add or remove files in the installation directory:
[Errno 2] No such file or directory: '/Users/blackbird/Library/Python/2.7/site-packages/test-easy-install-5544.write-test'
The installation directory you specified (via --install-dir, --prefix, or the distutils default setting) was:
/Users/blackbird/Library/Python/2.7/site-packages/
This directory does not currently exist. Please create it and try again, or choose a different installation directory (using the -d or --install-dir option).
我已进入我的库，并且Python文件夹不存在。显然我可以手动创建它，但这是否表明我做错了什么或者我错过了什么？