title: Pip install - do downloaded whl files persist & take disk space?
body: <p>While installing packages with <code>pip</code> in python, it downloads and installs a whl file, e.g. following file for pyqt5: </p>
  
  <pre><code>https://files.pythonhosted.org/packages/d4/bf/d884da8e2f7096d201c891d515eb6813a8e85df5eb6f5e12e867bf1d831c/PyQt5-5.11.3-5.11.2-cp35.cp36.cp37.cp38-abi3-manylinux1_x86_64.whl
  </code></pre>
  
  <p>After installation, does this file persist on disc and take space? </p>
  
  <p>If so, can it be removed to free space on disk? </p>
  
  <p>Also, is there a link regarding this anywhere in documentations?</p>