完整报错信息如下：
(open-mmlab) hench@hench-Precision-T3610:~$ pip install numpy WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError(1, '[SSL: WRONG_VERSION_NUMBER] wrong version number (_ssl.c:1091)'))': /simple/numpy/ WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError(1, '[SSL: WRONG_VERSION_NUMBER] wrong version number (_ssl.c:1091)'))': /simple/numpy/ WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', timeout('_ssl.c:1074: The handshake operation timed out'))': /simple/numpy/ WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError(1, '[SSL: WRONG_VERSION_NUMBER] wrong version number (_ssl.c:1091)'))': /simple/numpy/ WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLError(1, '[SSL: WRONG_VERSION_NUMBER] wrong version number (_ssl.c:1091)'))': /simple/numpy/ Could not fetch URL https://pypi.org/simple/numpy/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/numpy/ (Caused by SSLError(SSLError(1, '[SSL: WRONG_VERSION_NUMBER] wrong version number (_ssl.c:1091)'))) - skipping ERROR: Could not find a version that satisfies the requirement numpy ERROR: No matching distribution found for numpy Could not fetch URL https://pypi.org/simple/pip/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/pip/ (Caused by SSLError(SSLError(1, '[SSL: WRONG_VERSION_NUMBER] wrong version number (_ssl.c:1091)'))) - skipping (open-mmlab) hench@hench-Precision-T3610:~$
2021.1.18 更新：类似的连接错误也会发生在conda上
CondaHTTPError: HTTP 000 CONNECTION FAILED for url <https://repo.anaconda.com/pkgs/main/linux-64/current_repodata.json> Elapsed: -
2021.3.22 更新：再次发生conda下载错误
CondaHTTPError: HTTP 000 CONNECTION FAILED for url <https://repo.anaconda.com/pkgs/main/linux-64/current_repodata.json> Elapsed: - An HTTP error occurred when trying to retrieve this URL. HTTP errors are often intermittent, and a simple retry will get you on your way.
1 情况说明
我的Linux电脑是用代理proxy进行连接的。在ubuntu的设置-网络 设置过代理，也用代理设置代码给环境变量设置过代理。这是我export出来的环境变量。
declare -x http_proxy="http://henchli:****@www-proxy.waseda.jp:8080/" declare -x https_proxy="https://henchli:****@www-proxy.waseda.jp:8080/"
2. 在base环境中可以用pip下载包。
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2 错误说明
无法在非base由自己创建的虚拟环境中使用pip下载包。 把whl文件下载到本地然后用pip本地安装也是不行的。
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3 解决方法
关于这个问题，网上主要有两种解决思路。我先说不能解决我问题的第一种方法。
1. 各种花式--trusted-host（✘）
我第一次部分解决这个问题就是用了这个网页的方法，用的是douban的镜像。
但是这个方法只能下部分常见的包，比如numpy，scipy之类的。
如果douban没有收录这个包，比如pytorch和tensorflow，那就很麻烦了，比如要自己创建pip.conf然后写入--trusted-host，不同的网页还得改。
因此，我认为这些方法都不能从根本上解决问题。
2. 用export重新设置一次http代理[1] （✔）
export http_proxy="http://www-proxy.waseda.jp:8080" export https_proxy="http://www-proxy.waseda.jp:8080" # export http_proxy="http://<proxy.server>:<port>"
2021.1.13更新：碰到好几次过只改了http_proxy还是不行，然后把https_proxy也改了问题就解决了。
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