Getting line number from the exception object

Question

I have defined a custom Exception object and would like to get the line number of the exception.

class FlowException(Exception):
    pass

def something():
    print 2/3
    print 1/2
    print 2/0


try:
   something()
except Exception as e:
   raise FlowException("Process Exception", e)

Now, if there is a exception in something() it throws the FlowException but it does not give me the exact line number, How can I get the line number from FlowException(ie; it failed when it executed 2/0)?

Here is the output:--

raise FlowException("Process Exception", e)
__main__.FlowException: ('Process Exception', ZeroDivisionError('integer division or modulo by zero',))
[Finished in 0.4s with exit code 1]

On Python 3 when printing the FlowException you'd get an error like "while handling [original exception stack] encountered FlowException [flow exception stack]" — Bailey Parker
– Bailey Parker, Commented Jan 22, 2018 at 12:54
Possible duplicate of How to print the full traceback without halting the program? — Chris_Rands
– Chris_Rands, Commented Jan 22, 2018 at 12:59

user2390182 · Accepted Answer · 2018-01-22 13:01:48Z

6

The traceback object holds that info in the tb_lineno attribute:

import sys

# ...
except Exception as e:
   trace_back = sys.exc_info()[2]
   line = trace_back.tb_lineno
   raise FlowException("Process Exception in line {}".format(line), e)

answered Jan 22, 2018 at 13:01

user2390182

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1 Comment

pabouk - Ukraine stay strong Over a year ago

sys.exc_info()[2].tb_lineno is the line number inside the exception handler (try: block) not always what you want. To get the line where the exception emerged you need to go through the traceback or go directly to the end: traceback.extract_tb(sys.exc_info()[2])[-1].lineno

Diman · Accepted Answer · 2018-01-22 13:08:25Z

Tested on Python 3.6

class FlowException(Exception):
    pass

def something():
    raise ValueError

try:
   something()
except Exception as e:
    raise FlowException("Process Exception", e)

Output has line numbers:

Traceback (most recent call last):
  File "/Users/diman/PycharmProjects/invites/test.py", line 8, in <module>
    something()
  File "/Users/diman/PycharmProjects/invites/test.py", line 5, in something
    raise ValueError
ValueError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/diman/PycharmProjects/invites/test.py", line 10, in <module>
    raise FlowException("Process Exception", e)
__main__.FlowException: ('Process Exception', ValueError())

For Python 2 try using internal logger ".exception()" method instead of using monstrous "sys" module.

import logging
logger = logging.getLogger()

try:
    something()
except Exception as e:
    logger.exception(e)
    raise FlowException("Process Exception", e)

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