今天在安装一个第三方库时报如下错误
pip install --upgrade baostock
Could not fetch URL https://pypi.org/simple/baostock/: There was a problem confi
rming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max r
etries exceeded with url: /simple/baostock/ (Caused by SSLError(SSLCertVerificat
ionError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self si
gned certificate in certificate chain (_ssl.c:1045)'))) - skipping
当前python版本是3.7，网上查找说是python高版本需要验证ssl，可以添加--trusted-host domain来解决，于是赶紧尝试一下
pip install --trusted-host pypi.org --upgrade baostock
又报如下错误
Could not install packages due to an EnvironmentError: HTTPSConnectionPool(host=
'files.pythonhosted.org', port=443): Max retries exceeded with url: /packages/57
/f8/e909079851f6ea6685bb63ea143c66a0f4141fc3ce17e728ec908819ed54/baostock-0.8.5-
py3-none-any.whl (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFIC
ATE_VERIFY_FAILED] certificate verify failed: self signed certificate in certifi
cate chain (_ssl.c:1045)')))
原来是另一个域名files.pythonhosted.org也是https的，也需要指定为trusted-host才可以，问题是同时指定两个域名为trusted-host该怎么写呢？网上找了半天没找到，经过自己一番摸索，发现如下的写法可以
pip install --trusted-host pypi.org --trusted-host files.pythonhosted.org --upgrade baostock
如果是两个以上的域名以此类推，贡献给大家，希望对遇到同样问题的同学有所帮助。
