When I catch an exception, how do I get the
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 they’re 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 don’t 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 don’t leave our local labels/objects dangling # This still isn’t “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
Source
