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Docs: Align multiprocessing.shared_memory docs with Sphinx recommendations (#114103)

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- add :class: and :mod: markups where needed
- fix incorrect escaping of a star in ShareableList arg spec
- mark up parameters with stars: *val*
- mark up list of built-in types using list markup
- remove unneeded parentheses from :meth: markups
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Erlend E. Aasland 2024-01-16 13:35:35 +01:00 committed by GitHub
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Doc/library/multiprocessing.shared_memory.rst
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@ -20,8 +20,8 @@ and management of shared memory to be accessed by one or more processes
on a multicore or symmetric multiprocessor (SMP) machine. To assist with
the life-cycle management of shared memory especially across distinct
processes, a :class:`~multiprocessing.managers.BaseManager` subclass,
:class:`SharedMemoryManager`, is also provided in the
``multiprocessing.managers`` module.
:class:`~multiprocessing.managers.SharedMemoryManager`, is also provided in the
:mod:`multiprocessing.managers` module.
In this module, shared memory refers to "System V style" shared memory blocks
(though is not necessarily implemented explicitly as such) and does not refer
@ -47,9 +47,9 @@ copying of data.
As a resource for sharing data across processes, shared memory blocks
may outlive the original process that created them. When one process
no longer needs access to a shared memory block that might still be
needed by other processes, the :meth:`close()` method should be called.
needed by other processes, the :meth:`close` method should be called.
When a shared memory block is no longer needed by any process, the
:meth:`unlink()` method should be called to ensure proper cleanup.
:meth:`unlink` method should be called to ensure proper cleanup.
*name* is the unique name for the requested shared memory, specified as
a string. When creating a new shared memory block, if ``None`` (the
@ -62,7 +62,7 @@ copying of data.
memory block. Because some platforms choose to allocate chunks of memory
based upon that platform's memory page size, the exact size of the shared
memory block may be larger or equal to the size requested. When attaching
to an existing shared memory block, the ``size`` parameter is ignored.
to an existing shared memory block, the *size* parameter is ignored.
*track*, when enabled, registers the shared memory block with a resource
tracker process on platforms where the OS does not do this automatically.
@ -86,19 +86,19 @@ copying of data.
.. method:: close()
Closes the file descriptor/handle to the shared memory from this
instance. :meth:`close()` should be called once access to the shared
instance. :meth:`close` should be called once access to the shared
memory block from this instance is no longer needed. Depending
on operating system, the underlying memory may or may not be freed
even if all handles to it have been closed. To ensure proper cleanup,
use the :meth:`unlink()` method.
use the :meth:`unlink` method.
.. method:: unlink()
Deletes the underlying shared memory block. This should be called only
once per shared memory block regardless of the number of handles to it,
even in other processes.
:meth:`unlink()` and :meth:`close()` can be called in any order, but
trying to access data inside a shared memory block after :meth:`unlink()`
:meth:`unlink` and :meth:`close` can be called in any order, but
trying to access data inside a shared memory block after :meth:`unlink`
may result in memory access errors, depending on platform.
This method has no effect on Windows, where the only way to delete a
@ -145,7 +145,7 @@ instances::
The following example demonstrates a practical use of the :class:`SharedMemory`
class with `NumPy arrays <https://numpy.org/>`_, accessing the
same ``numpy.ndarray`` from two distinct Python shells:
same :class:`!numpy.ndarray` from two distinct Python shells:
.. doctest::
:options: +SKIP
@ -197,43 +197,43 @@ same ``numpy.ndarray`` from two distinct Python shells:
.. class:: SharedMemoryManager([address[, authkey]])
:module: multiprocessing.managers
A subclass of :class:`~multiprocessing.managers.BaseManager` which can be
A subclass of :class:`multiprocessing.managers.BaseManager` which can be
used for the management of shared memory blocks across processes.
A call to :meth:`~multiprocessing.managers.BaseManager.start` on a
:class:`SharedMemoryManager` instance causes a new process to be started.
:class:`!SharedMemoryManager` instance causes a new process to be started.
This new process's sole purpose is to manage the life cycle
of all shared memory blocks created through it. To trigger the release
of all shared memory blocks managed by that process, call
:meth:`~multiprocessing.managers.BaseManager.shutdown()` on the instance.
This triggers a :meth:`SharedMemory.unlink()` call on all of the
:class:`SharedMemory` objects managed by that process and then
stops the process itself. By creating ``SharedMemory`` instances
through a ``SharedMemoryManager``, we avoid the need to manually track
:meth:`~multiprocessing.managers.BaseManager.shutdown` on the instance.
This triggers a :meth:`~multiprocessing.shared_memory.SharedMemory.unlink` call
on all of the :class:`SharedMemory` objects managed by that process and then
stops the process itself. By creating :class:`!SharedMemory` instances
through a :class:`!SharedMemoryManager`, we avoid the need to manually track
and trigger the freeing of shared memory resources.
This class provides methods for creating and returning :class:`SharedMemory`
instances and for creating a list-like object (:class:`ShareableList`)
backed by shared memory.
Refer to :class:`multiprocessing.managers.BaseManager` for a description
Refer to :class:`~multiprocessing.managers.BaseManager` for a description
of the inherited *address* and *authkey* optional input arguments and how
they may be used to connect to an existing ``SharedMemoryManager`` service
they may be used to connect to an existing :class:`!SharedMemoryManager` service
from other processes.
.. method:: SharedMemory(size)
Create and return a new :class:`SharedMemory` object with the
specified ``size`` in bytes.
specified *size* in bytes.
.. method:: ShareableList(sequence)
Create and return a new :class:`ShareableList` object, initialized
by the values from the input ``sequence``.
by the values from the input *sequence*.
The following example demonstrates the basic mechanisms of a
:class:`SharedMemoryManager`:
:class:`~multiprocessing.managers.SharedMemoryManager`:
.. doctest::
:options: +SKIP
@ -251,9 +251,9 @@ The following example demonstrates the basic mechanisms of a
>>> smm.shutdown() # Calls unlink() on sl, raw_shm, and another_sl
The following example depicts a potentially more convenient pattern for using
:class:`SharedMemoryManager` objects via the :keyword:`with` statement to
ensure that all shared memory blocks are released after they are no longer
needed:
:class:`~multiprocessing.managers.SharedMemoryManager` objects via the
:keyword:`with` statement to ensure that all shared memory blocks are released
after they are no longer needed:
.. doctest::
:options: +SKIP
@ -269,38 +269,46 @@ needed:
... p2.join() # Wait for all work to complete in both processes
... total_result = sum(sl) # Consolidate the partial results now in sl
When using a :class:`SharedMemoryManager` in a :keyword:`with` statement, the
shared memory blocks created using that manager are all released when the
:keyword:`with` statement's code block finishes execution.
When using a :class:`~multiprocessing.managers.SharedMemoryManager`
in a :keyword:`with` statement, the shared memory blocks created using that
manager are all released when the :keyword:`!with` statement's code block
finishes execution.
.. class:: ShareableList(sequence=None, \*, name=None)
.. class:: ShareableList(sequence=None, *, name=None)
Provides a mutable list-like object where all values stored within are
stored in a shared memory block. This constrains storable values to
only the ``int`` (signed 64-bit), ``float``, ``bool``, ``str`` (less
than 10M bytes each when encoded as utf-8), ``bytes`` (less than 10M
bytes each), and ``None`` built-in data types. It also notably
differs from the built-in ``list`` type in that these lists can not
change their overall length (i.e. no append, insert, etc.) and do not
support the dynamic creation of new :class:`ShareableList` instances
stored in a shared memory block.
This constrains storable values to the following built-in data types:
* :class:`int` (signed 64-bit)
* :class:`float`
* :class:`bool`
* :class:`str` (less than 10M bytes each when encoded as UTF-8)
* :class:`bytes` (less than 10M bytes each)
* ``None``
It also notably differs from the built-in :class:`list` type
in that these lists can not change their overall length
(i.e. no :meth:`!append`, :meth:`!insert`, etc.) and do not
support the dynamic creation of new :class:`!ShareableList` instances
via slicing.
*sequence* is used in populating a new ``ShareableList`` full of values.
*sequence* is used in populating a new :class:`!ShareableList` full of values.
Set to ``None`` to instead attach to an already existing
``ShareableList`` by its unique shared memory name.
:class:`!ShareableList` by its unique shared memory name.
*name* is the unique name for the requested shared memory, as described
in the definition for :class:`SharedMemory`. When attaching to an
existing ``ShareableList``, specify its shared memory block's unique
name while leaving ``sequence`` set to ``None``.
existing :class:`!ShareableList`, specify its shared memory block's unique
name while leaving *sequence* set to ``None``.
.. note::
A known issue exists for :class:`bytes` and :class:`str` values.
If they end with ``\x00`` nul bytes or characters, those may be
*silently stripped* when fetching them by index from the
:class:`ShareableList`. This ``.rstrip(b'\x00')`` behavior is
:class:`!ShareableList`. This ``.rstrip(b'\x00')`` behavior is
considered a bug and may go away in the future. See :gh:`106939`.
For applications where rstripping of trailing nulls is a problem,
@ -326,12 +334,12 @@ shared memory blocks created using that manager are all released when the
.. method:: count(value)
Returns the number of occurrences of ``value``.
Returns the number of occurrences of *value*.
.. method:: index(value)
Returns first index position of ``value``. Raises :exc:`ValueError` if
``value`` is not present.
Returns first index position of *value*. Raises :exc:`ValueError` if
*value* is not present.
.. attribute:: format
@ -391,8 +399,8 @@ behind it:
>>> c.shm.close()
>>> c.shm.unlink()
The following examples demonstrates that ``ShareableList``
(and underlying ``SharedMemory``) objects
The following examples demonstrates that :class:`ShareableList`
(and underlying :class:`SharedMemory`) objects
can be pickled and unpickled if needed.
Note, that it will still be the same shared object.
This happens, because the deserialized object has

1
Doc/tools/.nitignore
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@ -57,7 +57,6 @@ Doc/library/logging.handlers.rst
Doc/library/lzma.rst
Doc/library/mmap.rst
Doc/library/multiprocessing.rst
Doc/library/multiprocessing.shared_memory.rst
Doc/library/optparse.rst
Doc/library/os.rst
Doc/library/pickle.rst