Python Iteration Error
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a try statement with an except clause that mentions a particular class, that clause also handles any exception classes type error python derived from that class (but not exception classes from which it is python filenotfounderror derived). Two exception classes that are not related via subclassing are never equivalent, even if they have the
Python Custom Exception
same name. The built-in exceptions listed below can be generated by the interpreter or built-in functions. Except where mentioned, they have an "associated value" indicating the detailed cause of
Python Exception Message
the error. This may be a string or a tuple of several items of information (e.g., an error code and a string explaining the code). The associated value is usually passed as arguments to the exception class's constructor. User code can raise built-in exceptions. This can be used to test an exception handler or to report an error python valueerror example condition "just like" the situation in which the interpreter raises the same exception; but beware that there is nothing to prevent user code from raising an inappropriate error. The built-in exception classes can be subclassed to define new exceptions; programmers are encouraged to derive new exceptions from the Exception class or one of its subclasses, and not from BaseException. More information on defining exceptions is available in the Python Tutorial under User-defined Exceptions. When raising (or re-raising) an exception in an except or finally clause __context__ is automatically set to the last exception caught; if the new exception is not handled the traceback that is eventually displayed will include the originating exception(s) and the final exception. When raising a new exception (rather than using a bare raise to re-raise the exception currently being handled), the implicit exception context can be supplemented with an explicit cause by using from with raise: raise new_exc from original_exc The expression following from must be an exception or N
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Python Exception Class Methods
Meta Discuss the workings and policies of this site About Us python 3 exceptions Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with python errno us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.2 million programmers, just https://docs.python.org/3/library/exceptions.html like you, helping each other. Join them; it only takes a minute: Sign up How to avoid StopIteration Error in python up vote 2 down vote favorite I have a line that is pulling in variables from multiple lists and I want it to avoid the StopIteration error that comes up so that it can move http://stackoverflow.com/questions/17317900/how-to-avoid-stopiteration-error-in-python onto the next line. At the moment I am using the break function, this avoids the StopIteration, but only gives me the first item in the list and it leaves a blank line after it, if i was to print it out. Here are two of my iterations that have the same problem. def compose_line5(self, synset_offset, pointer_list): self.line5 = '''''' for item in pointer_list: self.line5 += '''http://www.example.org/lexicon#'''+synset_offset+''' http://www.monnetproject.eu/lemon#has_ptr '''+pointer_list.next()+'''\n''' break return self.line5 def compose_line6(self, pointer_list, synset_list): self.line6 = '''''' for item in synset_list: self.line6 += '''http://www.example.org/lexicon#'''+pointer_list.next()+''' http://www.monnetproject.eu/lemon#pos '''+synset_list.next()+'''\n''' break return self.line6 This is the error I get without the break: Traceback (most recent call last): File "wordnet.py", line 225, in
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn http://stackoverflow.com/questions/13653783/how-to-catch-an-exception-in-the-for-loop-iterator more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags http://stackoverflow.com/questions/16465313/how-yield-catches-stopiteration-exception Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.2 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up How to catch an exception in the for loop iterator up vote 11 down vote favorite 2 This is a for loop in Python: for_stmt python exception ::= "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: import csv csv.field_size_limit(10) reader = csv.reader(open('test.csv', 'r')) for line in reader: print(line) with this file: foo,bar,baz xxx,veryverylong,yyy abc,def,ghi This aborts at the second line. I would like python iteration error a way to skip or log the failing lines and continue. python exception share|improve this question asked Nov 30 '12 at 21:57 Peter Eisentraut 19.7k44964 Similar question: stackoverflow.com/questions/7472786/…, but I can't change the generator in this case. –Peter Eisentraut Nov 30 '12 at 21:58 1 Why not just make a generator that calls the other generator but with a try/except? –Matthew Adams Nov 30 '12 at 22:00 2 @StevenRumbalski That's what I was thinking, but with csv.reader, it's not true (tried it myself). It raises a _csv.Error, but another call to next() on the reader will then just return the next after the error inducing line, and it will continue through to StopIteration as normal. –Silas Ray Nov 30 '12 at 22:09 1 can you clarify why try: print(line) except: continue does not work? –mehtunguh Nov 30 '12 at 22:12 3 @mehtunguh The raise happens in reader.next(), essentially, which is called in the for loop itself. print is after the fact, so try/catch around it won't work. –Silas Ray Nov 30 '12 at 22:17 | show 5 more comments 4 Answers 4 active oldest votes up vote 17 down vote If your inner iterable can be continued after an exception, all you need to wrap it is a trivial generator: def wrapper(gen): while True: try: yield next(gen) except StopIter
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.2 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up How yield catches StopIteration exception? up vote 6 down vote favorite 2 Why in the example function terminates: def func(iterable): while True: val = next(iterable) yield val but if I take off yield statement function will raise StopIteration exception? EDIT: Sorry for misleading you guys. I know what generators are and how to use them. Of course when I said function terminates I didn't mean eager evaluation of function. I just implied that when I use function to produce generator: gen = func(iterable) in case of func it works and returns the same generator, but in case of func2: def func2(iterable): while True: val = next(iterable) it raises StopIteration instead of None return or infinite loop. Let me be more specific. There is a function tee in itertools which is equivalent to: def tee(iterable, n=2): it = iter(iterable) deques = [collections.deque() for i in range(n)] def gen(mydeque): while True: if not mydeque: # when the local deque is empty newval = next(it) # fetch a new value and for d in deques: # load it to all the deques d.append(newval) yield mydeque.popleft() return tuple(gen(d) for d in deques) There is, in fact, some magic, because nested function gen has infinite loop without break statements. gen function terminates due to StopIteration exception when there is no items in it. But it terminates correctly (witho