CODEWITHSUNDEEP
pythonexception
David Board
David Board

Reputation: 349

What is the point of re-raising exceptions?

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

try:
    whatever()
except:
    raise

What is the purpose re-raising an exception? Surely an uncaught exception will just raise to the top anyway? i.e:

try:
    int("bad")
except:
    raise

has identical output to:

int("bad")

i.e. I get a ValueError in the console.

Upvotes: 5

Views: 1199

Answers (2)

TheLazyScripter
TheLazyScripter

Reputation: 2665

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

Upvotes: 2

ShadowRanger
ShadowRanger

Reputation: 155438

Your example code is pointless, but if you wanted to perform logging or cleanup that only occurs on failure, you could put that between the except: and the raise and you'd do that work and then proceed as if the original exception was bubbling normally.

Upvotes: 4

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