Python Throw Value Error
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Syntax For Generic Except Clause In Python
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Syntax For Raise Clause In Python
30 down vote favorite 1 I have this code which find the largest index of a specific character in a string , but I want it to raise a ValueError, when that specific character dose not occur in a string something like this contains('bababa', 'k') ValueError: could not find k in bababa How can I do this? this is the code def contains(string,char): list = python valueerror message [] for i in range(0,len(string)): if string[i] == char: list = list + [i] return list[-1] python string share|improve this question edited Dec 9 '10 at 1:31 aaronasterling 35.8k1084102 asked Dec 8 '10 at 23:08 user531225 2202512 What's your question? –Falmarri Dec 8 '10 at 23:09 1 how can I raise a ValueError –user531225 Dec 8 '10 at 23:10 2 Just like that, raise ValueError() hahaha –slezica Dec 8 '10 at 23:35 @user531225: Can you accept some another answer so that I can delete mine. Thanks :) –pyfunc Dec 9 '10 at 0:36 1 so basically you didn't bother to learn/find out "how to raise exceptions/errors in Python"...? –Erik Allik Sep 8 '12 at 8:57 | show 2 more comments 3 Answers 3 active oldest votes up vote 72 down vote raise ValueError('could not find %c in %s' % (ch,str)) share|improve this answer answered Dec 8 '10 at 23:10 NPE 255k36556746 add a comment| up vote 8 down vote >>> def contains(string, char): ... for i in xrange(len(string) - 1, -1, -1): ... if string[i] == char: ... return i ... raise ValueError("could not find %r in %r"
you have probably seen some. There are (at least) two distinguishable kinds of errors: syntax errors and exceptions. 8.1. Syntax Errors¶ Syntax errors, also known as parsing errors, are perhaps the most common kind of complaint you get
Is Nested Try Block Possible In Python
while you are still learning Python: >>> while True print('Hello world') File "
and VariablesOperatorsinput and raw_input via the keyboardConditional StatementsWhile LoopsFor LoopsFormatted outputOutput with PrintSequential Data TypesDictionariesSets and Frozen SetsShallow and Deep CopyFunctionsRecursion and Recursive FunctionsTests, DocTests, UnitTestsMemoization with DecoratorsPassing ArgumentsNamespacesGlobal http://www.python-course.eu/exception_handling.php vs. Local VariablesFile ManagementModular Programming and ModulesIntroduction in Regular ExpressionsRegular Expressions, AdvancedLambda Operator, Filter, Reduce and MapList ComprehensionGeneratorsException HandlingObject Oriented ProgrammingInheritance ExampleSlotsClasses and Class CreationRoad to https://infohost.nmt.edu/tcc/help/pubs/python/web/raise-statement.html MetaclassesMetaclassesMetaclass Example: Count Function Calls Exception from the Rule "There are two great rules of life, the one general and the other particular. The first is that in python everyone can in the end, get what he wants, if he only tries. That is the general rule. The particular rule is that every individual is, more or less, an exception to the rule." Samuel Butler Delicate Handling "The finest qualities of our nature, like the bloom on fruits, can be preserved only clause in python by the most delicate handling. Yet we do not treat ourselves nor one another thus tenderly." Henry David Thoreau Supported by: Python Training Courses in Canada This topic in German / Deutsche Übersetzung: AusnahmebehandlungPython 2.7This tutorial deals with Python Version 2.7This chapter from our course is available in a version for Python3: Exception HandlingClassroom Training Courses This website contains a free and extensive online tutorial by Bernd Klein. If you are interested in an instructor-led classroom training in Canada or the US, you may have a look at the Python courses by Bernd Klein at Bodenseo © kabliczech - Fotolia.com Overview of Python courses by Bernd Klein. The Truth in Errors "The first step towards amendment is the recognition of error." Seneca "The world always makes the assumption that the exposure of an error is identical with the discovery of truth - that the error and truth are simply opposite. They are nothing of the sort. W
program can't really proceed normally. For an overview, see Section 25, “Exceptions: Error signaling and handling”. There are three forms of the raise statement: raise raise E1 raise E1, E2 The first form is equivalent to “raise None,None” and the second form is equivalent to “raise E1
, None”. Each form raises an exception of a given type and with a given value. The type and value depend on how many expressions you provide: E1
E2
Exception typeException valueNoneNone Re-raise the current exception, if any. This might be done, for example, inside an except, else, or finally block; see Section 23.8, “The try statement: Anticipate exceptions”. classNone E1
E1()
class instance of E1
E1
E2
classtupleE1
E1
(*E2) classnone of the aboveE1
E1
(E2) instanceNone type(E1
) E1
The current recommended practice is to use a raise statement of this form: raise E(...) where E
is some class derived from the built-in Exception class: you can use one of the built-in exceptions, or you can create your own exception classes. For classes derived from Exception, the constructor takes one argument, an error message—that is, a string explaining why the exception was raised. The resulting instance makes that message available as an attribute named .message. Example: >>> try: ... raise ValueError('The day is too frabjous.') ... except ValueError as x: ... pass ... >>> type(x)