title: How does pip3 knows it should install packages into the virtual environment, when using symlinks rather than copies?
body: <p>How does <code>pip3 install</code> or <code>python3 -m  pip install</code> knows it should install packages into the virtual environment's <code>lib/python3.8/site-packages</code> directory?</p>
  <p>In particular, <code>python3</code> is symlinked as follows:</p>
  <pre><code>$ ls -la bin/python3
  lrwxr-xr-x  1 admin  staff    22B Jun 23 14:07 bin/python3@ -&gt; /usr/local/bin/python3
  </code></pre>
  <p>I've considered the <code>VIRTUAL_ENV</code> environment variable, but unsetting it doesn't seem to change how <code>pip3</code> behaves.</p>
  <p>Anyone knows?</p>