[Python-Dev] cpython (3.3): Add examples for opener argument of open (#13424).

[Georg Brandl]

Am 03.11.2012 22:10, schrieb eric.araujo:
> http://hg.python.org/cpython/rev/17b094c08600
> changeset:   80219:17b094c08600
> branch:      3.3
> parent:      80214:e6d0951f412a
> user:        Éric Araujo <merwok at netwok.org>
> date:        Sat Nov 03 17:06:52 2012 -0400
> summary:
>   Add examples for opener argument of open (#13424).
> 
> Patch by Guillaume Pratte.
> 
> files:
>   Doc/library/functions.rst |  30 +++++++++++++++++++++++++++
>   Doc/library/io.rst        |   3 ++
>   Misc/ACKS                 |   1 +
>   3 files changed, 34 insertions(+), 0 deletions(-)
> 
> 
> diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
> --- a/Doc/library/functions.rst
> +++ b/Doc/library/functions.rst
> @@ -935,6 +935,36 @@
>     :mod:`os.open` as *opener* results in functionality similar to passing
>     ``None``).
>  
> +   The following example is an alternative implementation for opening files
> +   for exclusive writing.  If we did not have support for the ``'x'`` mode,
> +   we could implement it with this opener::
> +
> +      >>> import os
> +      >>> def open_exclusive(path, mode):
> +      ...     return os.open(path, mode | os.O_CREAT | os.O_EXCL)
> +      ...
> +      >>> filename = 'spam.txt'
> +      >>> fp = open(filename, 'w', opener=open_exclusive)
> +      >>> fp2 = open(filename, 'w', opener=open_exclusive)
> +      Traceback (most recent call last):
> +        ...
> +      FileExistsError: [Errno 17] File exists: 'spam.txt'
> +
> +   This other example uses the :ref:`dir_fd` parameter of the
> +   :func:`os.open` function to open a file relative to a given directory::

Please heed your Sphinx warnings: the :ref:`dir_fd` needs a link caption, since
it can't autogenerate one (the dir_fd anchor does not point to a heading).

Georg