Raising, Reraising and Chaining Exceptions in Python #python

raising_exceptions.py

#!/usr/bin/env python

# if you are handling an exception, you can raise another exception in 4 ways:

# EXCEPTION RERAISE/RETHROW
# this reraises the same exception, in this case
# it just means you couldn't handle the exception
try:
    raise Exception
except Exception as e:
    raise e
    # raise # this is equivalent and you won't need to bind the exception
    
# EXCEPTION HANDLING EXCEPTION
# this raises another exception in the handling of the first exception
# python will recognise this and report it as so
# only do this if you really have an exception while handling an exception
try:
    raise Exception
except Exception as e:
    raise Exception

# EXCEPTION OVERRIDE
# this overrides the exception with a whole new exception
# use this when you are wrapping a library of internal exceptions and presenting a transformed external exceptions
try:
    raise Exception
except Exception as e:
    raise Exception from None

# EXCEPTION CHAIN
# this raises a new exception and chains the new exception with the old exception
# use this when your code represents an onion of different layers each capable of handling different exceptions
try:
    raise Exception
except Exception as e:
    raise Exception from e