如果pip出现换了源都不行的操作，那么你可以试试这种方法

我遇到过的两个错误

第一个：

WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', timeout('_ssl.c:732: The handshake operation timed out',))': /simple/%20--trusted-host%20pypi.douban.com/pyqt5-tools/

 第二个：

 The repository located at pypi.tuna.tsinghua.edu.cn is not a trusted or secure host and is being ignored. If this repository is available via HTTPS it is recommended to use HTTPS instead, otherwise you may silence this warning and allow it anyways with '--trusted-host pypi.tuna.tsinghua.edu.cn'.
  Could not find a version that satisfies the requirement pyqt5 (from versions: )
No matching distribution found for pyqt5

 

只需要以下这条命令，轻松解决

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

注意需要讲package换成你需要的包

这时候安装就成功了

 具体为什么这样子就成功了我目前也不知道，有大佬看到可以解释一下