pip安装包报错：PS C:\Users\Administrator\Desktop> pip install request ERROR: Could not find a version that satisfies the requirement request (from versions: none)

PS C:\Users\Administrator\Desktop> pip install request
ERROR: Could not find a version that satisfies the requirement request (from versions: none)
ERROR: No matching distribution found for request

出现这种报错有以下几种可能性：

1.pip版本过低，需要更新

python -m pip install --upgrade pip

2.代理服务器处于打开状态，需要关闭

3.换源。我刚开始用清华源，失败，改用豆瓣源，OK。

 pip install requests  -i http://pypi.douban.com/simple/ --trusted-host pypi.douban.com

具体做法是 pip install 你需要的包的名字  -i http://pypi.douban.com/simple/ --trusted-host pypi.douban.com