What is the point of re-raising exceptions?

Question

So I\'ve seen mention elsewhere of using the following to re-raise an exception.

try:
    whatever()
except:
    raise

What is the purpose

Answer 1

Imagine the following code.

A little setup: You are responsible for maintaining a huge database of information for example, and any loss of data would be catastrophic!

huge_dictionary = {'lots_of_important':['stuffs']}
try:
    check_data(new_data) #make sure the data is in the correct format
    huge_dictionary['lots_of_important'].append(new_data)
except:
    data_writer.backup(huge_dictionary)
    data_writer.close()
    #and any other last second changes
    raise