python – When I catch an exception, how do I get the type, file, and line number?

python – When I catch an exception, how do I get the type, file, and line number?

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)

Simplest form that worked for me.

import traceback

try:
    print(4/0)
except ZeroDivisionError:
    print(traceback.format_exc())

Output

Traceback (most recent call last):
  File /path/to/file.py, line 51, in <module>
    print(4/0)
ZeroDivisionError: division by zero

Process finished with exit code 0

python – When I catch an exception, how do I get the type, file, and line number?

Source (Py v2.7.3) for traceback.format_exception() and called/related functions helps greatly. Embarrassingly, I always forget to Read the Source. I only did so for this after searching for similar details in vain. A simple question, How to recreate the same output as Python for an exception, with all the same details? This would get anybody 90+% to whatever theyre looking for. Frustrated, I came up with this example. I hope it helps others. (It sure helped me! 😉

import sys, traceback

traceback_template = Traceback (most recent call last):
  File %(filename)s, line %(lineno)s, in %(name)s
%(type)s: %(message)sn # Skipping the actual line item

# Also note: we dont walk all the way through the frame stack in this example
# see hg.python.org/cpython/file/8dffb76faacc/Lib/traceback.py#l280
# (Imagine if the 1/0, below, were replaced by a call to test() which did 1/0.)

try:
    1/0
except:
    # http://docs.python.org/2/library/sys.html#sys.exc_info
    exc_type, exc_value, exc_traceback = sys.exc_info() # most recent (if any) by default

    
    Reason this _can_ be bad: If an (unhandled) exception happens AFTER this,
    or if we do not delete the labels on (not much) older versions of Py, the
    reference we created can linger.

    traceback.format_exc/print_exc do this very thing, BUT note this creates a
    temp scope within the function.
    

    traceback_details = {
                         filename: exc_traceback.tb_frame.f_code.co_filename,
                         lineno  : exc_traceback.tb_lineno,
                         name    : exc_traceback.tb_frame.f_code.co_name,
                         type    : exc_type.__name__,
                         message : exc_value.message, # or see traceback._some_str()
                        }

    del(exc_type, exc_value, exc_traceback) # So we dont leave our local labels/objects dangling
    # This still isnt completely safe, though!
    # Best (recommended) practice: replace all exc_type, exc_value, exc_traceback
    # with sys.exc_info()[0], sys.exc_info()[1], sys.exc_info()[2]

    print
    print traceback.format_exc()
    print
    print traceback_template % traceback_details
    print

In specific answer to this query:

sys.exc_info()[0].__name__, os.path.basename(sys.exc_info()[2].tb_frame.f_code.co_filename), sys.exc_info()[2].tb_lineno