Issue #12797: Added custom opener parameter to builtin open() and FileIO.open().

2 files changed, 20 insertions, 2 deletions

diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index f63cea4..f9af3d8 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -776,7 +776,7 @@ are always available.  They are listed here in alphabetical order.
    :meth:`__index__` method that returns an integer.
 
 
-.. function:: open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True)
+.. function:: open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)
 
    Open *file* and return a corresponding stream.  If the file cannot be opened,
    an :exc:`OSError` is raised.
@@ -883,6 +883,15 @@ are always available.  They are listed here in alphabetical order.
    closed.  If a filename is given *closefd* has no effect and must be ``True``
    (the default).
 
+   A custom opener can be used by passing a callable as *opener*. The underlying
+   file descriptor for the file object is then obtained by calling *opener* with
+   (*file*, *flags*). *opener* must return an open file descriptor (passing
+   :mod:`os.open` as *opener* results in functionality similar to passing
+   ``None``).
+
+   .. versionchanged:: 3.3
+      The *opener* parameter was added.
+
    The type of file object returned by the :func:`open` function depends on the
    mode.  When :func:`open` is used to open a file in a text mode (``'w'``,
    ``'r'``, ``'wt'``, ``'rt'``, etc.), it returns a subclass of
diff --git a/Doc/library/io.rst b/Doc/library/io.rst
index 0bcf687..1da7e4c 100644
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -458,7 +458,7 @@ I/O Base Classes
 Raw File I/O
 ^^^^^^^^^^^^
 
-.. class:: FileIO(name, mode='r', closefd=True)
+.. class:: FileIO(name, mode='r', closefd=True, opener=None)
 
    :class:`FileIO` represents an OS-level file containing bytes data.
    It implements the :class:`RawIOBase` interface (and therefore the
@@ -479,6 +479,15 @@ Raw File I/O
    The :meth:`read` (when called with a positive argument), :meth:`readinto`
    and :meth:`write` methods on this class will only make one system call.
 
+   A custom opener can be used by passing a callable as *opener*. The underlying
+   file descriptor for the file object is then obtained by calling *opener* with
+   (*name*, *flags*). *opener* must return an open file descriptor (passing
+   :mod:`os.open` as *opener* results in functionality similar to passing
+   ``None``).
+
+   .. versionchanged:: 3.3
+      The *opener* parameter was added.
+
    In addition to the attributes and methods from :class:`IOBase` and
    :class:`RawIOBase`, :class:`FileIO` provides the following data
    attributes and methods: