Python 3 Io Error
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a try statement with an except clause that mentions a particular class, that clause also handles any exception classes derived from that class (but valueerror python not exception classes from which it is derived). Two exception classes that are
Python Custom Exception
not related via subclassing are never equivalent, even if they have the same name. The built-in exceptions listed below
Python Raise Valueerror
can be generated by the interpreter or built-in functions. Except where mentioned, they have an "associated value" indicating the detailed cause of the error. This may be a string or a tuple
Python Exception Message
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 condition "just like" the situation in which the interpreter raises the same exception; but beware python filenotfounderror 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 None. It will be set as __cause__ on the raised exception. Setting __cause__ also implicitly sets the __suppress_context__ attribute to True, so that using raise <
This module never needs to be imported explicitly: the exceptions are provided in the built-in namespace as well as the exceptions module. For class exceptions, in a try statement with an except clause that mentions a particular class, that clause also handles any exception classes python exception class methods derived from that class (but not exception classes from which it is derived). Two exception classes that are not related python attributeerror object has no attribute via subclassing are never equivalent, even if they have the 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" https://docs.python.org/3/library/exceptions.html indicating the detailed cause of the error. This may be a string or a tuple containing several items of information (e.g., an error code and a string explaining the code). The associated value is the second argument to the raise statement. If the exception class is derived from the standard root class BaseException, the associated value is present as the exception instance's args attribute. User https://docs.python.org/2/library/exceptions.html code can raise built-in exceptions. This can be used to test an exception handler or to report an error 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. The following exceptions are only used as base classes for other exceptions. exception BaseException¶ The base class for all built-in exceptions. It is not meant to be directly inherited by user-defined classes (for that, use Exception). If str() or unicode() is called on an instance of this class, the representation of the argument(s) to the instance are returned, or the empty string when there were no arguments. New in version 2.5. args¶ The tuple of arguments given to the exception constructor. Some built-in exceptions (like IOError) expect a certain number of arguments and assign a special meaning to the elements of this tuple, while othe
a try statement with an except clause that mentions a particular class, that clause also handles any exception classes derived from that class (but not exception classes from which it is derived). Two exception classes https://docs.python.org/3.3/library/exceptions.html that are not related via subclassing are never equivalent, even if they have the http://stackoverflow.com/questions/29347790/difference-between-ioerror-and-oserror 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 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 python exception 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 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 sub-classed to define new exceptions; programmers python 3 io are encouraged to at least derive new exceptions from the Exception class and not 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 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 None. It will be set as __cause__ on the raised exception. Setting __cause__ also implicitly sets the __suppress_context__ attribute to True, so that using raise new_exc from None effectively replaces the old exception with the new one for display purposes (e.g. converting KeyError to AttributeError, while leaving the old exception available in __context__ for introspection when debugging. The default traceback display code shows these chained exceptions in addition to the traceback for the exception itself. An explicitly chained exception in __cause__ is always shown when present. An implicitly chained exception in __context
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 Difference between IOError and OSError? up vote 5 down vote favorite 1 I am always getting confused on whether a function would raise an IOError or OSError (or both?). What is the principle rule behind these exception types, what is the difference between them and when is which raised? I've initially thought OSError is for things like permission denial, but opening a file without permissions will raise an IOError. python exception python-2.x share|improve this question edited Mar 30 '15 at 13:44 asked Mar 30 '15 at 13:42 Niklas R 4,6771042105 4 Changed in version 3.3: EnvironmentError, IOError, WindowsError, VMSError, socket.error, select.error and mmap.error have been merged into OSError. E.g. just throw OSError and forget about IOError. –Martijn Pieters♦ Mar 30 '15 at 13:44 @MartijnPieters Thanks, I've added the Python 2 tag. Just throwing OSError sounds good to me, yet I'm always having trouble to know when a function like shutil.copyfile() or os.access() would raise IOError or OSError (always have to look it up) –Niklas R Mar 30 '15 at 13:44 2 Also see python.org/dev/peps/pep-3151 for the background on this, it'll help put the two exceptions into perspective. –Martijn Pieters♦ Mar 30 '15 at 13:44 1 If you are getting confused by it - well, that's one reason to switch to Python 3 then. –Antti Haapala Mar 30 '15 at 13:46 2 @AnttiHaapala I do use Python 3 for standalone projects, but its a different story in an embedded Python environment. :) –Niklas R Mar 30 '15 at 13:47 | show 1 more comment 1 Answer 1 active oldest votes up vote 7 down vote accepted There is very little difference between the two types. In fact, even the core Python developers agreed that ther