Python Raise Error Types
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a try statement with an except clause that mentions a particular class, that clause also handles any
Python Exception Message
exception classes derived from that class (but not exception classes from python custom exception which it is derived). Two exception classes that are not related via subclassing are never equivalent, even python raise valueerror 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"
Python Filenotfounderror
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 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
Python Exception Class Methods
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. 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 n
you have probably seen some. There are (at least) two distinguishable kinds of errors: syntax errors and exceptions. 8.1. python errno Syntax Errors¶ Syntax errors, also known as parsing errors, are perhaps the
Python Attributeerror Object Has No Attribute
most common kind of complaint you get while you are still learning Python: >>> while True print('Hello python exception stack trace world') File "
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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 Re-raise exception with a different type and message, preserving existing information up vote 41 down vote favorite 12 I'm writing a module and want to have a unified exception hierarchy for the exceptions that it can raise (e.g. inheriting from a FooError abstract class for all the foo module's specific exceptions). This allows users of the module to catch those particular exceptions and handle them distinctly, if needed. But many of the exceptions raised from the module are raised because of some other exception; e.g. failing at some task because of an OSError on a file. What I need is to “wrap” the exception caught such that it has a different type and message, so that information is available further up the propagation hierarchy by whatever catches the exception. But I don't want to lose the existing type, message, and stack trace; that's all useful information for someone trying to debug the problem. A top-level exception handler is no good, since I'm trying to decorate the exception before it makes its way further up the propagation stack, and the top-level handler is too late. This is partly solved by deriving my module foo's specific exception types from the existing type (e.g. class FooPermissionError(OSError, FooError)), but that doesn't make it any easier to wrap the existing exception instance in a new type, nor modify the message. Python's PEP 3134 “Exception Chaining and Embedded Tracebacks” discusses a change accepted in Python 3.0 for “chaining” exception objects, to indicate that a new exception was raised during the handling of an existing exception. What I'm trying to do is related: I need it also working in earlier Python versions, and I need it not for chaining, but only for polymorphism. What is the right way to do this? python exception-handling polymorphism share|improve this question edited Feb 4 at 5:14 asked Mar 30 '09 at 5:04 bignose 10.1k63561 Exceptions already are completely polymorphic -- they're all subclasses of Exception. What are you trying to do? "Different message" is fairly trivial with a top-level except