Python - Conditionally Catching Exceptions

Question

Is it possible to conditionally catch exceptions in python? I would like to be able to write a function so that the caller can decide who handles the exception.

Basically, I would like something like this:

def my_func(my_arg, handle_exceptions):     try:         do_something(my_arg)     except Exception as e if handle_exceptions:         print "my_func is handling the exception" 

I know I could write some kludgy code that does what I want, but I want a pythonic answer if there is one.
Thanks.

Answer 1

You can re-raise the exception if you don't want to handle it:

def my_func(my_arg, handle_exceptions):     try:         do_something(my_arg)     except Exception, e:         if not handle_exceptions:             # preserve prior stack trace             raise              # Or, if you dont care about the stack prior to this point             #raise Exception(e)              # similarly, you can just re-raise e.  The stack trace will start here though.             #raise e         else:             print "my_func is handling the exception" 

---

Another option is to create your own exceptions that subclass Exception (or a specific exception like urllib2.HTTPError) and then only catch/throw (raise) your custom exception:

class MyException(Exception):     def __init__(self, message):         self.message = message  class MyExceptionTwo(Exception):     def __init__(self, message):         self.message = message     def __repr__(self):         return "Hi, I'm MyExceptionTwo.  My error message is: %s" % self.message  def something():     if not tuesday:         raise MyException("Error: it's not Tuesday.")     else:         raise MyExceptionTwo("Error: it's Tuesday.")  def my_func(my_arg):     try:         something()     except MyException, e:         print e.message     # Will pass MyExceptionTwo up the call chain  def my_other_func():     try:         my_func(your_arg)     except MyExceptionTwo, e:         print str(e)     # No need to catch MyException here since we know my_func() handles it     # but we can hadle MyExceptionTwo here