title: ValueError: could not convert string to float in simple code
body: <pre><code>       # -*- coding: cp1250 -*-
  print ('euklides alpha 1.0')
  a = raw_input('podaj liczbę A  : ')
  b = raw_input('podaj liczbę B  : ')
  
  a = float('a')
  b = float('b')
  
  if 'a'=='b':
      print 'a'
  elif 'a' &gt; 'b':
      while 'a' &gt; 'b':
          print('a'-'b')
          if 'a'=='b': break
          if 'a' &gt; 'b': continue
  elif 'b' &gt; 'a':
      while 'b' &gt; 'a':
          print('b'-'a')
          if 'b'=='a': break
          if 'b' &gt; 'a': continue
  </code></pre>
  
  <p>So, this is a code, which I made few hours ago. Now I get a <code>ValueError: could not convert string to float: a</code>, and I have no idea why. Can you explain it to me? I'm a beginner.</p>