title: What's the difference between all of the os.popen() methods?
body: <p>I was looking at the <a href="http://www.python.org/doc/2.5.2/lib/module-popen2.html" rel="noreferrer">Python documentation</a> and saw that there are 4-5 different versions of popen(), e.g. os.popen(), os.popen2(), etc. </p>
  
  <p>Apart from the fact that some include <em>stderr</em> while others don't, what are the differences between them and when would you use each one? The documentation didn't really explain it very well.</p>