title: Difference between len and size
body: <p>I found two ways to determine how many elements are in a variable…
  I always get the same values for <code>len ()</code> and <code>size ()</code>. Is there a difference? Could <code>size ()</code> have come with an imported library (like <code>math</code>, <code>numpy</code>, <code>pandas</code>)?</p>
  
  <pre><code>asdf = range (10)
  print ( 'len:', len (asdf), 'versus size:', size (asdf) )
  
  asdf = list (range (10))
  print ( 'len:', len (asdf), 'versus size:', size (asdf) )
  
  asdf = np.array (range (10))
  print ( 'len:', len (asdf), 'versus size:', size (asdf) )
  
  asdf = tuple (range (10))
  print ( 'len:', len (asdf), 'versus size:', size (asdf) )
  </code></pre>