python - python3 re-raising an exception with custom attribute? -

here's code python2 needs ported:

try:   do_something_with_file(filename)  except:   exc_type, exc_inst, tb = sys.exc_info()   exc_inst.filename = filename   raise exc_type, exc_inst, tb 

with above code, can whole exception problematic input file checking whether exception has 'filename' attribute.

however python3's raise has been changed. 2to3 gave me above code:

except exception e:   et, ei, tb = sys.exc_info()   e.filename = filename   raise et(e).with_traceback(tb) 

which gives me error , don't think filename attribute preserved:

in __call__     raise et(e).with_traceback(tb) typeerror: function takes 5 arguments (1 given) 

what want passing exceptions transparently information track input file. miss python2's raise [exception_type[,exception_instance[,traceback]]] - how can in python3?

you can set __traceback__ attribute:

except exception e:     et, ei, tb = sys.exc_info()     ei.filename = filename     ei.__traceback__ = tb     raise ei 

or call .with_traceback() directly on old instance:

except exception e:     et, ei, tb = sys.exc_info()     ei.filename = filename     raise ei.with_traceback(tb) 

however, traceback automatically attached, there no need re-attach it, really.

see raise statement documentation:

a traceback object created automatically when exception raised , attached __traceback__ attribute, writable.

in specific case, perhaps wanted different exception instead, context?

class filenameexception(exception):     filename = none     def __init__(self, filename):         super().__init__(filename)         self.filename = filename  try:     something(filename) except exception e:     raise filenameexception(filename) e 

this create chained exception, both exceptions printed if uncaught, , original exception available newexception.__context__.