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#3525: 3.0 exception changes in tutorial.

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Georg Brandl 2008-08-08 06:50:56 +00:00
parent 1e3830a178
commit f5f2630db6
2 changed files with 16 additions and 20 deletions
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34
Doc/tutorial/errors.rst
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@ -1,4 +1,4 @@
. _tut-errors:
.. _tut-errors:
*********************
Errors and Exceptions
@ -131,8 +131,8 @@ the exception (allowing a caller to handle the exception as well)::
f = open('myfile.txt')
s = f.readline()
i = int(s.strip())
except IOError as (errno, strerror):
print("I/O error({0}): {1}".format(errno, strerror))
except IOError as err:
print("I/O error: {0}".format(err))
except ValueError:
print("Could not convert data to an integer.")
except:
@ -162,25 +162,21 @@ When an exception occurs, it may have an associated value, also known as the
exception's *argument*. The presence and type of the argument depend on the
exception type.
The except clause may specify a variable after the exception name (or tuple).
The variable is bound to an exception instance with the arguments stored in
The except clause may specify a variable after the exception name. The
variable is bound to an exception instance with the arguments stored in
``instance.args``. For convenience, the exception instance defines
:meth:`__getitem__` and :meth:`__str__` so the arguments can be accessed or
printed directly without having to reference ``.args``.
But use of ``.args`` is discouraged. Instead, the preferred use is to pass a
single argument to an exception (which can be a tuple if multiple arguments are
needed) and have it bound to the ``message`` attribute. One may also
instantiate an exception first before raising it and add any attributes to it as
desired. ::
:meth:`__str__` so the arguments can be printed directly without having to
reference ``.args``. One may also instantiate an exception first before
raising it and add any attributes to it as desired. ::
>>> try:
... raise Exception('spam', 'eggs')
... except Exception as inst:
... print(type(inst)) # the exception instance
... print(inst.args) # arguments stored in .args
... print(inst) # __str__ allows args to be printed directly
... x, y = inst # __getitem__ allows args to be unpacked directly
... print(inst) # __str__ allows args to be printed directly,
... # but may be overridden in exception subclasses
... x, y = inst.args # unpack args
... print('x =', x)
... print('y =', y)
...
@ -190,7 +186,7 @@ desired. ::
x = spam
y = eggs
If an exception has an argument, it is printed as the last part ('detail') of
If an exception has arguments, they are printed as the last part ('detail') of
the message for unhandled exceptions.
Exception handlers don't just handle exceptions if they occur immediately in the
@ -202,10 +198,10 @@ indirectly) in the try clause. For example::
...
>>> try:
... this_fails()
... except ZeroDivisionError as detail:
... print('Handling run-time error:', detail)
... except ZeroDivisionError as err:
... print('Handling run-time error:', err)
...
Handling run-time error: integer division or modulo by zero
Handling run-time error: int division or modulo by zero
.. _tut-raising: