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From: Aaron Watters <arw@big.att.com>
Newsgroups: comp.object,comp.lang.eiffel,comp.lang.c++,comp.lang.beta,comp.lang.java,comp.lang.sather,comp.lang.python
Subject: Re: What Should An Exception Handling Do? -- Clarification of rules
Date: Tue, 26 Mar 1996 18:10:33 -0500
Organization: AT&T
Lines: 67
Message-ID: <31587969.5259@big.att.com>
References: <Doq3sv.MzA@research.att.com> <1996Mar25.160702.14229@schbbs.mot.com> <4j948d$t3d@trumpet.uni-mannheim.de>
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Someone way up in this thread wanted to know what errors
were good for other than aborting...

Some uses for exceptions, other than as aborts, in python:

# get or create a data item from an archive
try:
    person = people[name]
except KeyError:
    person = people[name] = Person(name)

# ignore broken urls, but follow the good ones (stolen from a spyder)
urllistpending = [starturl]
goodurls = []
while urllistpending:
    thisurl = urllistpending[-1]  # get/delete last pending
    del urllistpending[-1]
    try:
       text = thisurl.get_text()  # try to follow the url
    except IOError:
       continue # url broken...
    else:
       goodurls.append(thisurl)   # good url, add embedded refs
       newurls = text.urls_mentioned()
       urllistpending = urllistpending + newurls

# Do an endless loop, use error to return terminating value
#  from anywhere, even deeply embedded calls (stolen from pickle.py)
try:
    while 1:
        ........ blah blah blah .....
except STOP, value # note: STOP is unique to this module
    result = value

# is a path a directory? (even if it doesn't exist?) (from dospath.py)
def isdir(path):
        try:
                st = os.stat(path)
        except os.error:
                return 0
        else:
                return stat.S_ISDIR(st[stat.ST_MODE])

# print the object using the .print method, if there is one or use default printing
# otherwise
try:
    print object.print()
except AttributeError:
    print object

# and the best of all, if you have a socket module, use it, else use
# the Mac module SOCKS, or the WinSock module, if available
try:
   import socket
except ImportError:
   try:
       import SOCKS
       socket = SOCKS
   except ImportError:
       import WinSock
       socket = WinSock

-- Aaron Watters
====
        "If falling in love is anything like learning how to spell, I don't
 want to  do it.  It takes too long."
     Glenn, age 7 (mailed all over the world, original attribution lost).