title: What is a None value?
body: <p>I have been studying Python, and I read a chapter which describes the <code>None</code> value, but unfortunately this book isn't very clear at some points. I thought that I would find the answer to my question, if I share it there.</p>
  
  <p>I want to know what the <code>None</code> value <em>is</em> and what do you use it for?</p>
  
  <p>And also, I don't get this part of the book:</p>
  
  <blockquote>
    <p>Assigning a value of <code>None</code> to a variable is one way to reset it to
    its original, empty state.</p>
  </blockquote>
  
  <p>What does that mean?</p>
  
  <p>The answers were great, although I didn't understand most of answers due to my low knowledge of the computer world (I haven't learned about classes, objects, etc.). What does this sentence mean?</p>
  
  <blockquote>
    <p>Assigning a value of <code>None</code> to a variable is one way to reset it
    to its original, empty state.</p>
  </blockquote>
  
  <p>Final:</p>
  
  <p>Finally I've got my answer from looking to different answers. I must appreciate all the people who put their times to help me (especially Martijn Pieters and DSM), and I wish that I could choose all answers as the best, but the selection is limited to one. All of the answers were great.</p>