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| -rw-r--r-- | Doc/library/exceptions.rst | 38 |
1 files changed, 26 insertions, 12 deletions
diff --git a/Doc/library/exceptions.rst b/Doc/library/exceptions.rst index bf7be21..528febd 100644 --- a/Doc/library/exceptions.rst +++ b/Doc/library/exceptions.rst @@ -18,12 +18,10 @@ 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" -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 usually passed to the exception -class's constructor. If the exception class is derived from the standard root -class :exc:`BaseException`, the associated value is present as the exception -instance's :attr:`args` attribute. +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 exception handler or to report an error condition "just like" the situation in which the @@ -38,16 +36,32 @@ defining exceptions is available in the Python Tutorial under The following exceptions are used mostly as base classes for other exceptions. -.. XXX document with_traceback() - .. 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 :exc:`Exception`). If + inherited by user-defined classes (for that, use :exc:`Exception`). If :func:`bytes` or :func:`str` 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. All arguments are stored in :attr:`args` - as a tuple. + representation of the argument(s) to the instance are returned, or the empty + string when there were no arguments. + + .. attribute:: args + + The tuple of arguments given to the exception constructor. Some built-in + exceptions (like :exc:`IOError`) expect a certain number of arguments and + assign a special meaning to the elements of this tuple, while others are + usually called only with a single string giving an error message. + + .. method:: with_traceback(tb) + + This method sets *tb* as the new traceback for the exception and returns + the exception object. It is usually used in exception handling code like + this:: + + try: + ... + except SomeException: + tb = sys.exc_info()[2] + raise OtherException(...).with_traceback(tb) .. exception:: Exception |