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I can't figure out how to handle exception for python 'with' statement. If I have a code: with open("a.txt") as f: print f.readlines() I really want to handle 'file not found exception' in order to do something. But I can't write. with open("a.txt") as f: print f.readlines() except: print 'oops' and can't write
Never use exceptions for flow-control. Exceptions exist for exceptional situations: events that are not a part of normal execution. Consider 'find' on a string returning -1 if the pattern isn't found, but indexing beyond the end of a string raises an exception. Not finding the string is normal execution. Handle exceptions at the level that ...
Jun 13, 2022 · How do I manually throw/raise an exception in Python? Use the most specific Exception constructor that semantically fits your issue. Be specific in your message, e.g.: raise ValueError('A very specific bad thing happened.') Don't raise generic exceptions. Avoid raising a generic Exception. To catch it, you'll have to catch all other more ...
Aug 21, 2022 · You can either catch the base-class exception, which will handle all cases: try: r = requests.get (url, params= {'s': thing}) except requests.exceptions.RequestException as e: # This is the correct syntax raise SystemExit (e) Or you can catch them separately and do different things.
Handling the exception is the way to go: try: gotdata = dlist[1] except IndexError: gotdata = 'null'. Of course you could also check the len() of dlist; but handling the exception is more intuitive. edited Oct 27, 2017 at 12:25. answered Aug 10, 2012 at 13:17. ThiefMaster.
This is OK if running in the main thread; however, having the following code does not work: try: threadClass = TheThread (param1, param2, etc.) threadClass.start () ##### **Exception takes place here** except: print "Caught an exception". In the thread class itself, I tried to re-throw the exception, but it does not work.
Jun 20, 2022 · @aaronsteers it does use the captured exception; in an exception handler the current exception is available via the sys.exc_info() function and the traceback.print_exc() function gets it from there. You’d only ever need to pass in an exception explicitly when not handling an exception or when you want to show info based on a different exception.
Apr 6, 2021 · to point out that you know what you're doing. All exceptions stem from BaseException, and those you're meant to catch day-to-day (those that'll be thrown for the programmer) inherit too from Exception. except (Exception) never catches KeyboardInterrupt errors. as e doesn't have anything to do with it.
This is a for loop in Python: for_stmt ::= "for" target_list "in" expression_list ":" suite Normally, when yielding a value from the expression_list raises an exception, the loop aborts. Is there an elegant way (short of rewriting the loop using while True or something similar) to catch this exception and continue the loop? Here is an example:
fName = [FILE TO OPEN] if os.path.exists (fName): with open (fName, 'rb') as f: #add you code to handle the file contents here. elif IOError: print "Unable to open file: "+str (fName) This way you can attempt to open the file, but if it doesn't exist (if it raises an IOError), alert the user!
