How to use nested try/catch in python?

Question

I have following code, in which i have to handle exception for 2 statements,

2nd line and 4th line

if(re.search("USN:.*MediaRenderer", datagram, flags=re.IGNORECASE)):
    deviceXML = re.search("LOCATION:(.*.xml)", datagram, flags=re.IGNORECASE).group(1)   # this line            
    root = ElementTree.fromstring(urllib2.urlopen(XMLLocation).read())                
    friendlyName = root.find('.//{}friendlyName'.format(Server.namespace)).text   # this line
    if not friendlyName in deviceList.keys():
       deviceList[friendlyName] = host
    self.model.setStringList(deviceList.keys())

How can i use nested try/catch here

I tried following way:

if(re.search("USN:.*MediaRenderer", datagram, flags=re.IGNORECASE)):
        try:
            deviceXML = re.search("LOCATION:(.*.xml)", datagram, flags=re.IGNORECASE).group(1)            
            root = ElementTree.fromstring(urllib2.urlopen(XMLLocation).read())                
            try:
                friendlyName = root.find('.//{}friendlyName'.format(Server.namespace)).text
                print "\n fname = ", friendlyName
                if not friendlyName in deviceList.keys():
                    deviceList[friendlyName] = host
                self.model.setStringList(deviceList.keys())                
        except:
            pass

This is giving me indentation error for except line

ron rothman · Accepted Answer · 2014-05-19 14:09:18Z

4

Your inner try block is missing an except clause (which is required).

try:
    # do something risky

    try:
        # do another risky thing
    except:  # <-- this is required
        # handle the inner exception

except Exception as exc:
    # handle outer exception

But you may want to restructure your code to have two separate blocks. It will be cleaner that way and easier to understand/maintain.

if(re.search("USN:.*MediaRenderer", datagram, flags=re.IGNORECASE)):
    try:
        deviceXML = re.search("LOCATION:(.*.xml)", datagram, flags=re.IGNORECASE).group(1)            
        root = ElementTree.fromstring(urllib2.urlopen(XMLLocation).read())                

    except:
        # return, break, etc.

    # no exception from previous block; proceed with processing

    try:
        friendlyName = root.find('.//{}friendlyName'.format(Server.namespace)).text
        print "\n fname = ", friendlyName
        if not friendlyName in deviceList.keys():
            deviceList[friendlyName] = host
        self.model.setStringList(deviceList.keys())                

    except Exception as exc:
        # do something with the error here

edited May 19, 2014 at 14:09

answered May 19, 2014 at 14:04

ron rothman

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2 Comments

Patrick Over a year ago

having 2 except is not giving me any o/p

ron rothman Over a year ago

Okay. Can't help you with no output unless you post your code. (But this answer illustrates how to use nested exceptions.)

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