Cameron Simpson <c...@cskk.id.au> writes: > On 28Jun2019 12:17, Cecil Westerhof <ce...@decebal.nl> wrote: >>Chris Angelico <ros...@gmail.com> writes: >>> On Fri, Jun 28, 2019 at 7:33 PM Cecil Westerhof <ce...@decebal.nl> wrote: >>>> I have a tkinter program where I have a function generate_report >>>> which >>>> in a try block calls the function append_row. This function has also a >>>> try block. When they get an exception they give message. But when >>>> append_row has already given a message then generate_report should >>>> not. To implement this I use the following class: >>>> >>>> class AlreadyHandledException(Exception): >>>> pass >>>> >>>> Then in append_row I have: >>>> except Exception as err: >>>> messagebox.showerror(error_str, >>>> error_append + '\n\n\n\n' + str(err)) >>>> raise AlreadyHandledException() >>>> >>>> And in generate_report I have: >>>> except Exception as err: >>>> if type(err).__name__ != "AlreadyHandledException": >>>> messagebox.showerror(error_str, >>>> error_generate + '\n\n\n\n' + str(err)) >>>> progress.pack_forget() >>>> >>>> Is this an acceptable way, or should I do it differently? >>> >>> Well, first off, I would use two separate except clauses, rather than >>> a type check. >> >>You are completely right. >> >>> But are you able to just NOT catch the exception inside >>> append_row? Let it be handled at the top level only. >> >>I am giving different messages. I changed the top part to: >> except AlreadyHandledException: >> pass >> except Exception as err: >> messagebox.showerror(error_str, error_generate + '\n\n\n\n' + >> str(err)) >> progress.lower() > > For contrast, another approach. > > By catching AlreadyHandledException and just going "pass" you're > effectively swalling that exception. For your purpose, that works. > > However, in a since, why raise an exception you _know_ you're going to > deliberately ignore?
I am not. I am using it to quit generating the report. Just ignoring that I could not append a record does not sound correct to me. Yes they got a message that something went wrong. But if there is still a generated report, things will go wrong. > What if you have append_row return a Boolean? True on success, False on > failure but situation handled (i.e. append_row has shown an error, or > whatever recovery you adopt). And keep the uncaught exceptions for the > _unhandled_ situation. The "exceptional" situation. > > Example: > > def append_row(...): > ... > try: > ...stuff... > except ExpectedExceptionHere as err: > messagebox.showerror(....) > ...maybe some cleanup... > return False > ... > return True > > Then your generate_report code goes: > > try: > appended = append_row(....) > except Exception as err: > messagebox.showerror(....) > else: > if appended: > hooray! > else: > unhappy, but continuing And that is exactly what I not want to do. -- Cecil Westerhof Senior Software Engineer LinkedIn: http://www.linkedin.com/in/cecilwesterhof -- https://mail.python.org/mailman/listinfo/python-list
