[Tutor] exception details

[Marilyn Davis]

Hi,

I'm trying to get a strong handle on exception mechanism details.

Note that there are three try/except's and that the 1st 2 work
fine.  But the third one doesn't catch the random exception
generated.

Do I have a typo?

Thank you for any help you can give.

Marilyn Davis

#!/usr/bin/env python2.2
'''Ways to get more info about your caught exception.'''

import exceptions # to get a list of built-in exceptions
import random
import sys  # gives info -- you can use the traceback module but
            # it uses sys.

def ok(msg):
    raise ValueError, msg

def fun(msg):
    '''Raises a random built-in exception.'''
    excepts = dir(exceptions)
    while excepts[-1][0] == '_':
        # Getting rid of __doc__ and __name__
        excepts.pop()
    raise_this = excepts[random.randrange(len(excepts))]
    print 'Raising', str(raise_this), 'To', msg
    raise raise_this, msg

if __name__ == '__main__':
    try:
        ok('this works ok')
    except Exception, exception:
        print 'exception.args = ', exception.args
        print 'exception = ', exception

    try:
        fun('catch with "except:" on random exception works')
    except:
        print 'Caught: sys.exc_type =', sys.exc_type,\
              'sys.exc_value =', sys.exc_value
        print 'sys.exc_traceback =', sys.exc_traceback
        print sys.exc_info()

    try:
        fun('''catch with "Exception, exception: on random exception doesn't work"''')
    except Exception, exception:
        print 'exception.args = ', exception.args
        print 'exception = ', exception

############################################################
# OUTPUT:
# bash-2.05a$ ./x.py
# exception.args =  ('this works ok',)
# exception =  this works ok
# Raising UnboundLocalError To catch with "except:" on random exception works
# Caught: sys.exc_type = UnboundLocalError sys.exc_value = catch with "except:" on random exception works
# sys.exc_traceback = <traceback object at 0x81522f4>
# ('UnboundLocalError', 'catch with "except:" on random exception works', <traceback object at 0x81522f4>)
# Raising Exception To catch with "Exception, exception: on random exception doesn't work"
# Traceback (most recent call last):
#   File "./x.py", line 37, in ?
#     fun('''catch with "Exception, exception: on random exception doesn't work"''')
#   File "./x.py", line 19, in fun
#     raise raise_this, msg
# Exception: catch with "Exception, exception: on random exception doesn't work"
# bash-2.05a$ 


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