title: Round to significant figures in python
body: <p>I want to round like this 42949672 -> 42949700, 2147483647 -> 2147480000, 4252017622 -> 4252020000 etc.</p>
  
  <p>I tried to use following , but only works for the first one. How can I make a more general one? thanks</p>
  
  <pre><code>round(42949672, -2)
  </code></pre>