pip安装pypdf及opencv相关包失败，请求技术支持

问题场景 #

执行pip install pypdf时安装失败，报错信息如下：

WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7f012437ffa0>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution')': /simple/pypdf/
WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7f01243a0310>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution')': /simple/pypdf/
WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7f01243a0670>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution')': /simple/pypdf/
WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7f01243a0820>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution')': /simple/pypdf/
WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7f01243a09d0>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution')': /simple/pypdf/
ERROR: Could not find a version that satisfies the requirement pypdf (from versions: none)
ERROR: No matching distribution found for pypdf
WARNING: There was an error checking the latest version of pip.

误以为问题出在opencv上，尝试执行以下命令仍出现相同的"Could not find a version that satisfies the requirement"错误：

pip install opencv-python
pip install python-opencv
pip install opencv-contrib-python

问题根源 #

报错中的Temporary failure in name resolution是域名解析失败，说明你的机器无法正常连接到PyPI服务器，和opencv没有任何关系。pip找不到包是因为连不上PyPI服务器，根本没获取到包的版本信息，并非包本身不存在。

解决步骤 #

• 检查基础网络连接：执行ping pypi.org测试能否访问PyPI服务器，如果不通，排查本地网络是否正常（比如能否正常打开网页），是否有防火墙、网络策略限制。
• 更换国内PyPI镜像源安装：如果网络正常但访问PyPI慢或失败，直接使用国内镜像源安装，示例命令：

  pip install pypdf -i https://pypi.tuna.tsinghua.edu.cn/simple
  

  安装opencv相关包同理：

  pip install opencv-python -i https://pypi.tuna.tsinghua.edu.cn/simple
  

• 修复系统DNS配置：如果域名解析持续失败，尝试修改系统DNS服务器为公共DNS，比如8.8.8.8或114.114.114.114。
• 检查代理设置：如果机器使用代理，确保pip已配置正确的代理参数，示例：

  pip install pypdf --proxy http://代理IP:端口号
  

  若不需要代理，可取消代理环境变量：

  unset HTTP_PROXY
  unset HTTPS_PROXY
  

内容的提问来源于stack exchange，提问作者user20176030