title: Why shouldn't I use PyPy over CPython if PyPy is 6.3 times faster?
body: <p>I've been hearing a lot about the <a href="http://en.wikipedia.org/wiki/PyPy" rel="noreferrer">PyPy</a> project. They claim it is 6.3 times faster than the <a href="http://en.wikipedia.org/wiki/CPython" rel="noreferrer">CPython</a> interpreter on <a href="http://speed.pypy.org" rel="noreferrer">their site</a>.</p>
  
  <p>Whenever we talk about dynamic languages like Python, speed is one of the top issues. To solve this, they say PyPy is 6.3 times faster.</p>
  
  <p>The second issue is parallelism, the infamous <a href="http://en.wikipedia.org/wiki/Global_Interpreter_Lock" rel="noreferrer">Global Interpreter Lock</a> (GIL). For this, PyPy says it <a href="http://pypy.org/tmdonate.html" rel="noreferrer">can give GIL-less Python</a>.</p>
  
  <p>If PyPy can solve these great challenges, what are its weaknesses that are preventing wider adoption? That is to say, what's preventing someone like me, a typical Python developer, from switching to PyPy <em>right now</em>? </p>