Python Raise Error With Message
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Python Raise Valueerror
hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join syntax for generic except clause in python 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 Manually raising (throwing) an
Python Exception Message
exception in Python up vote 800 down vote favorite 189 How can I raise an exception in Python so that it can later be caught via an except block? python exception exception-handling share|improve this question edited Feb 3 '15 at 14:37 DavidRR 5,20472747 asked Jan 12 '10 at 21:07 TIMEX 41.2k201525826 add a comment| 3 Answers 3 active oldest votes up vote 787 down vote syntax for raise clause in python accepted 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 do this: Avoid raising a generic Exception, to catch it, you'll have to catch all other more specific exceptions that subclass it. Hiding bugs raise Exception('I know Python!') # don't, if you catch, likely to hide bugs. For example: def demo_bad_catch(): try: raise ValueError('represents a hidden bug, do not catch this') raise Exception('This is the exception you expect to handle') except Exception as error: print('caught this error: ' + repr(error)) >>> demo_bad_catch() caught this error: ValueError('represents a hidden bug, do not catch this',) Won't catch and more specific catches won't catch the general exception: def demo_no_catch(): try: raise Exception('general exceptions not caught by specific handling') except ValueError as e: print('we will not catch e') >>> demo_no_catch() Traceback (most recent call last): File "
Pages Local Site Map ------------------------ Rename Page Delete Page ------------------------ ------------------------ Remove Spam Revert to this revision ------------------------ SlideShow User Login Handling Exceptions The simplest way to handle exceptions is with a "try-except" block: 1 (x,y) = (5,0) 2 try: 3 z = x/y 4 except ZeroDivisionError: 5 print "divide by zero" If you wanted
Python Exception Stack Trace
to examine the exception from code, you could have: 1 (x,y) = (5,0) 2
Python Print Exception
try: 3 z = x/y 4 except ZeroDivisionError as e: 5 z = e # representation: " Error: %s
program can't really proceed normally. For an overview, see Section 25, “Exceptions: Error signaling and handling”. https://infohost.nmt.edu/tcc/help/pubs/python/web/raise-statement.html 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 python raise 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 clause in python 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)