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| author | Shahriar Heidrich <smheidrich@weltenfunktion.de> | 2022-10-05 00:36:04 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2022-10-05 00:36:04 (GMT) |
| commit | 395b66a0ae5237eec195ca97daaaf8563706ed34 (patch) | |
| tree | 0a6751b70611516c72cd83f0ffd8211cd8f916b3 | |
| parent | 76449350b3467b85bcb565f9e2bf945bd150a66e (diff) | |
| download | cpython-395b66a0ae5237eec195ca97daaaf8563706ed34.zip cpython-395b66a0ae5237eec195ca97daaaf8563706ed34.tar.gz cpython-395b66a0ae5237eec195ca97daaaf8563706ed34.tar.bz2 | |
gh-97654: Add auto exception chaining example to tutorial (#97703)
Add auto exception chaining example to tutorial
| -rw-r--r-- | Doc/tutorial/errors.rst | 28 |
1 files changed, 23 insertions, 5 deletions
diff --git a/Doc/tutorial/errors.rst b/Doc/tutorial/errors.rst index 57919e3..67bb195 100644 --- a/Doc/tutorial/errors.rst +++ b/Doc/tutorial/errors.rst @@ -284,8 +284,27 @@ re-raise the exception:: Exception Chaining ================== -The :keyword:`raise` statement allows an optional :keyword:`from<raise>` which enables -chaining exceptions. For example:: +If an unhandled exception occurs inside an :keyword:`except` section, it will +have the exception being handled attached to it and included in the error +message:: + + >>> try: + ... open("database.sqlite") + ... except OSError: + ... raise RuntimeError("unable to handle error") + ... + Traceback (most recent call last): + File "<stdin>", line 2, in <module> + FileNotFoundError: [Errno 2] No such file or directory: 'database.sqlite' + <BLANKLINE> + During handling of the above exception, another exception occurred: + <BLANKLINE> + Traceback (most recent call last): + File "<stdin>", line 4, in <module> + RuntimeError: unable to handle error + +To indicate that an exception is a direct consequence of another, the +:keyword:`raise` statement allows an optional :keyword:`from<raise>` clause:: # exc must be exception instance or None. raise RuntimeError from exc @@ -311,9 +330,8 @@ This can be useful when you are transforming exceptions. For example:: File "<stdin>", line 4, in <module> RuntimeError: Failed to open database -Exception chaining happens automatically when an exception is raised inside an -:keyword:`except` or :keyword:`finally` section. This can be -disabled by using ``from None`` idiom: +It also allows disabling automatic exception chaining using the ``from None`` +idiom:: >>> try: ... open('database.sqlite') |