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#10856: document (Base)Exception.args better.

This commit is contained in:
Georg Brandl 2011-01-07 18:28:45 +00:00
parent 7603fa07a8
commit fb6fd5d019
1 changed files with 26 additions and 12 deletions
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38
Doc/library/exceptions.rst
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@ -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