title: How to configure PIP per config file to use a proxy (with authentification)?
body: <p>I used to set up environment evariables http_proxy and https_proxy (with user + password) in the past to use Pip (on Windows) behind a corporate proxy. But recently I needed to tell Pip to use a proxy without setting up environment variables as this conflicted with git configuration in combination with SSL Certificates which I get to work only by removing environment variables for proxy.</p>
  
  <p>Fortunately you can configure PIP with an pip.ini file as described here: <a href="https://pip.pypa.io/en/stable/user_guide/#config-file" rel="noreferrer">https://pip.pypa.io/en/stable/user_guide/#config-file</a></p>
  
  <p>The detailed answer to my own question follows below.</p>