title: Mimic C preprocessor with Python/Ruby?
body: <p>I need to mimic the preprocessor feature of C with Python.</p>
  
  <p>If I want to run the debug release, I use as follows with C</p>
  
  <pre><code>#ifdef DEBUG
  printf(...)
  #endif
  </code></pre>
  
  <p>I just use -DDEBUG or similar to trigger it on or off.</p>
  
  <p>What method can I use for Python/Ruby? 
  I mean, what should I do to control the behavior of python/ruby scripts in such a way that I can change a variable that affects all the script files in a project? </p>