Python exception handling - line number

Question

I\'m using python to evaluate some measured data. Because of many possible results it is difficult to handle or possible combinations. Sometimes an error happens during the

Answer 1

Solution, printing filename, linenumber, line itself and exception descrpition:

import linecache
import sys

def PrintException():
    exc_type, exc_obj, tb = sys.exc_info()
    f = tb.tb_frame
    lineno = tb.tb_lineno
    filename = f.f_code.co_filename
    linecache.checkcache(filename)
    line = linecache.getline(filename, lineno, f.f_globals)
    print 'EXCEPTION IN ({}, LINE {} "{}"): {}'.format(filename, lineno, line.strip(), exc_obj)


try:
    print 1/0
except:
    PrintException()

Output:

EXCEPTION IN (D:/Projects/delme3.py, LINE 15 "print 1/0"): integer division or modulo by zero

Answer 2

The simplest way is just to use:

import traceback
try:
    <blah>
except IndexError:
    traceback.print_exc()

or if using logging:

import logging
try:
    <blah>
except IndexError as e:
    logging.exception(e)

Answer 3

I would suggest using the python logging library, it has two useful methods that might help in this case.

1. logging.findCaller()

   • findCaller(stack_info=False) - Reports just the line number for the previous caller leading to the exception raised
   • findCaller(stack_info=True) - Reports the line number & stack for the previous caller leading to the exception raised

2. logging.logException()

   • Reports the line & stack within the try/except block that raised the exception

For more info checkout the api https://docs.python.org/3/library/logging.html

Answer 4

I always use this snippet

import sys, os

try:
    raise NotImplementedError("No error")
except Exception as e:
    exc_type, exc_obj, exc_tb = sys.exc_info()
    fname = os.path.split(exc_tb.tb_frame.f_code.co_filename)[1]
    print(exc_type, fname, exc_tb.tb_lineno)

for different views and possible issues you can refer When I catch an exception, how do I get the type, file, and line number?

Answer 5

To simply get the line number you can use sys, if you would like to have more, try the traceback module.

import sys    
try:
    [][2]
except IndexError:
    #  Python 2
    print 'Error on line {}'.format(sys.exc_info()[-1].tb_lineno)
    #  Python 3
    print("Error on line {}".format(sys.exc_info()[-1].tb_lineno))

prints:

Error on line 3

---

Example from the traceback module documentation:

import sys, traceback

def lumberjack():
    bright_side_of_death()

def bright_side_of_death():
    return tuple()[0]

try:
    lumberjack()
except IndexError:
    exc_type, exc_value, exc_traceback = sys.exc_info()
    print "*** print_tb:"
    traceback.print_tb(exc_traceback, limit=1, file=sys.stdout)
    print "*** print_exception:"
    traceback.print_exception(exc_type, exc_value, exc_traceback,
                              limit=2, file=sys.stdout)
    print "*** print_exc:"
    traceback.print_exc()
    print "*** format_exc, first and last line:"
    formatted_lines = traceback.format_exc().splitlines()
    print formatted_lines[0]
    print formatted_lines[-1]
    print "*** format_exception:"
    print repr(traceback.format_exception(exc_type, exc_value,
                                          exc_traceback))
    print "*** extract_tb:"
    print repr(traceback.extract_tb(exc_traceback))
    print "*** format_tb:"
    print repr(traceback.format_tb(exc_traceback))
    print "*** tb_lineno:", exc_traceback.tb_lineno

Answer 6

I use the traceback which is simple and robust:

import traceback

try:
    raise ValueError()
except:
    print(traceback.format_exc())

Out:

Traceback (most recent call last):
  File "catch.py", line 4, in <module>
    raise ValueError()
ValueError