diff options
| -rw-r--r-- | Doc/tutorial/errors.rst | 19 |
1 files changed, 10 insertions, 9 deletions
diff --git a/Doc/tutorial/errors.rst b/Doc/tutorial/errors.rst index 0ce9646..efe44da 100644 --- a/Doc/tutorial/errors.rst +++ b/Doc/tutorial/errors.rst @@ -273,15 +273,15 @@ Exception Chaining ================== The :keyword:`raise` statement allows an optional :keyword:`from` which enables -chaining exceptions by setting the ``__cause__`` attribute of the raised -exception. For example:: +chaining exceptions. For example:: - raise RuntimeError from OSError + # exc must be exception instance or None. + raise RuntimeError from exc This can be useful when you are transforming exceptions. For example:: >>> def func(): - ... raise IOError + ... raise IOError ... >>> try: ... func() @@ -297,12 +297,11 @@ This can be useful when you are transforming exceptions. For example:: <BLANKLINE> Traceback (most recent call last): File "<stdin>", line 4, in <module> - RuntimeError + RuntimeError: Failed to open database -The expression following the :keyword:`from` must be either an exception or -``None``. Exception chaining happens automatically when an exception is raised -inside an exception handler or :keyword:`finally` section. Exception chaining -can be disabled by using ``from None`` idiom: +Exception chaining happens automatically when an exception is raised inside an +:keyword:`except` or :keyword:`finally` section. Exception chaining can be +disabled by using ``from None`` idiom: >>> try: ... open('database.sqlite') @@ -313,6 +312,8 @@ can be disabled by using ``from None`` idiom: File "<stdin>", line 4, in <module> RuntimeError +For more information about chaining mechanics, see :ref:`bltin-exceptions`. + .. _tut-userexceptions: |