title: Unable to make a factorial function in Python
body: <p><strong>My code</strong></p>
  
  <pre><code>import sys
  
  number=int(sys.argv[1])
  
  if number == 0
      fact=1
  else
      fact=number
  for (x=1; x&lt;number; x++)
      fact*=x;             // mistake probably here
  
  print fact
  </code></pre>
  
  <p>I get the error</p>
  
  <pre><code>File "factorial.py", line 5
      if number == 0
                   ^
  SyntaxError: invalid syntax
  </code></pre>
  
  <p><strong>How can you make a factorial function in Python?</strong></p>