title: Checking arguments in python
body: <p>Hello I am a noobie programmer who just started coding.
  Suppose a function exists:</p>
  
  <pre class="lang-py prettyprint-override"><code>def ask(a,b,c):
  </code></pre>
  
  <p>So how can I return a string if the user doesn't give 3 arguments while calling the function?
  for example:
  <code>ask(1,2)</code>
  or <code>ask(1,2,3,4)</code>?</p>