title: python how to re-raise an exception which is already caught?
body: <pre><code>import sys
  def worker(a):
      try:
          return 1 / a
      except ZeroDivisionError:
          return None
  
  
  def master():
      res = worker(0)
      if not res:
          print(sys.exc_info())
          raise sys.exc_info()[0]
  </code></pre>
  
  <p>As code piece above, I have a bunch of functions like worker. They already have their own try-except block to handle exceptions. And then one master function will call each worker. Right now, sys.exc_info() return all None to 3 elements, how to re-raise the exceptions in the master function? 
  I am using Python 2.7</p>
  
  <p>One update:
    I have more than 1000 workers and some worker has very complex logic, they may deal multiple types of exceptions at same time. So my question is can I just raise those exceptions from master rather than edit works?</p>