title: How do I check if a string is a negative number before passing it through int()?
body: <p>I'm trying to write something that checks if a string is a number or a negative. If it's a number (positive or negative) it will passed through int(). Unfortunately isdigit() won't recognize it as a number when "-" is included.</p>
  
  <p>This is what I have so far:</p>
  
  <pre><code>def contestTest():
  # Neutral point for struggle/tug of war/contest
  x = 0
  
  while -5 &lt; x &lt; 5:
      print "Type desired amount of damage."
      print x
      choice = raw_input("&gt; ")
  
      if choice.isdigit():
          y = int(choice)
          x += y
      else:
          print "Invalid input."
  
  if -5 &gt;= x:
      print "x is low. Loss."
      print x
  elif 5 &lt;= x:
      print "x is high. Win."
      print x
  else:
      print "Something went wrong."
      print x
  </code></pre>
  
  <p>The only solution I can think of is some separate, convoluted series of statements that I might squirrel away in a separate function to make it look nicer. I'd be grateful for any help!</p>