title: Why does QtWidgets.QApplication require sys.argv?
body: <p>Hello guys i am learning pyqt5 from a series of tutorials at youtube and i didn't get why <code>QtWidgets.QApplication</code> have the argument <code>sys.argv</code> i am not familiar with <code>sys</code> library i read the documentation but still have no clue so sorry i know this question is kind of a noobish.</p>
  
  <pre><code>import sys
  from PyQt5 import QtWidgets
  
  
  def window():
      app = QtWidgets.QApplication(sys.argv)
      w=QtWidgets.QWidget()
      w.show()
      sys.exit(app.exec_())
  
  window()
  </code></pre>