How to catch message of finally exception clause in python?

Question

I know how to catch exceptions and print the message they returned:

class SelfDefinedException(Exception): pass

try:
    message = "Hello World!"
    raise SelfDefinedException(message)
except MyDefinedException, e:
    print "MyDefinedException", e

This works good so far.

But how can I catch and print the message in a 'finally' clause?

class SelfDefinedException(Exception): pass

try:
    message = "Hello World!"
    raise SelfDefinedException(message)
except MyDefinedException, e:
    print "MyDefinedException", e
finally:
    # What goes here? So I can see what went wrong?

From several answers I understand, that this is not possible. Is it ok to do something like this?

class SelfDefinedException(Exception): pass

try:
    message = "Hello World!"
    raise SelfDefinedException(message)
except MyDefinedException, e:
    print "MyDefinedException", e
except Exception, e:
    # Hopefully catches all messages except for the one of MyDefinedException
    print "Unexpected Exception raised:", e

@Winston, I implemented a handling of my own Exceptions I raise, but I want to be informed if somehow another exception was raised, that I did not expect. See my edit. — Aufwind
– Aufwind, Commented Jun 21, 2011 at 22:50
yes, if you want to catch all other exceptions, just keep listing them with more except clauses. see documentation — Dirk
– Dirk, Commented Jun 21, 2011 at 22:57

Nathan Romano · Accepted Answer · 2011-06-21 22:42:10Z

4

the code in the finally block will always be evaluated. check to see what went wrong in the catch block

answered Jun 21, 2011 at 22:42

Nathan Romano

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2 Comments

Aufwind Over a year ago

I understand, that finally catches any Exception except for SelfDefinedException in my example. But how do I get to visualize in the finally` block the Message and the type of exception raised in the try block?

thehouse Over a year ago

@Druss, The finally clause doesn't catch any exceptions. It is always executed even in the successful case

Dirk · Accepted Answer · 2011-06-21 22:45:10Z

4

According to the documentation, you can't:

The exception information is not available to the program during execution of the finally clause.

Best to check in the except block.

answered Jun 21, 2011 at 22:45

Dirk

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Comments

Winston Ewert · Accepted Answer · 2011-06-21 23:10:14Z

2

To catch anything at all use:

try:
    foo()
except:
    print sys.exc_info()
    raise

But this is almost always the wrong thing to do. If you don't what kind of exception happened there isn't anything you can do about it. If this happens your program should shut down and provide as much information as possible about what happened.

answered Jun 21, 2011 at 23:10

Winston Ewert

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Comments

Daniel Backman · Accepted Answer · 2013-07-10 10:04:48Z

1

I needed similar thing but in my case to always cleanup some resources when no exception occurred. The below solution example worked for me and should also answer the question.

    caught_exception=None
    try:
      x = 10/0
      #return my_function()
    except Exception as e:
      caught_exception = e
    finally:
      if caught_exception:
         #Do stuff when exception
         raise # re-raise exception
      print "No exception"

answered Jul 10, 2013 at 10:04

Daniel Backman

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2 Comments

GingerPlusPlus Over a year ago

You'd better move #Do stuff when exception to except, and print "No exception" to else

Daniel Backman Over a year ago

@GingerPlusPlus I see your point, but the construct answers the question "But how can I catch and print the message in a 'finally' clause?"

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