Python: Getting the error message of an exception

Question

In python 2.6.6, how can I capture the error message of an exception.

IE:

response_dict = {} # contains info to response under a django view.
try:
    plan.save()
    response_dict.update({'plan_id': plan.id})
except IntegrityError, e: #contains my own custom exception raising with custom messages.
    response_dict.update({'error': e})
return HttpResponse(json.dumps(response_dict), mimetype="application/json")

This doesnt seem to work. I get:

IntegrityError('Conflicts are not allowed.',) is not JSON serializable

Answer 1

Pass it through str() first.

response_dict.update({'error': str(e)})

Also note that certain exception classes may have specific attributes that give the exact error.

Answer 2

Everything about str is correct, yet another answer: an Exception instance has message attribute, and you may want to use it (if your customized IntegrityError doesn't do something special):

except IntegrityError, e: #contains my own custom exception raising with custom messages.
    response_dict.update({'error': e.message})

Answer 3

You should use unicode instead of string if you are going to translate your application.

BTW, Im case you're using json because of an Ajax request, I suggest you to send errors back with HttpResponseServerError rather than HttpResponse:

from django.http import HttpResponse, HttpResponseServerError
response_dict = {} # contains info to response under a django view.
try:
    plan.save()
    response_dict.update({'plan_id': plan.id})
except IntegrityError, e: #contains my own custom exception raising with custom messages.
    return HttpResponseServerError(unicode(e))

return HttpResponse(json.dumps(response_dict), mimetype="application/json")

and then manage errors in your Ajax procedure. If you wish I can post some sample code.

Answer 4

Suppose you raise error like this

raise someError("some error message")

and 'e' is catched error instance

str(e) returns:

[ErrorDetail(string='some error message', code='invalid')]

but if you want "some error message" only

e.detail

will gives you that (actually gives you a list of str which includes "some error message")

Answer 5

This works for me:

def getExceptionMessageFromResponse( oResponse ):
    #
    '''
    exception message is burried in the response object,
    here is my struggle to get it out
    '''
    #
    l = oResponse.__dict__['context']
    #
    oLast = l[-1]
    #
    dLast = oLast.dicts[-1]
    #
    return dLast.get( 'exception' )