python-docs-fr/extending/newtypes.po

# Copyright (C) 2001-2018, Python Software Foundation
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msgstr ""
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#: extending/newtypes.rst:7
msgid "Defining Extension Types: Assorted Topics"
msgstr ""

#: extending/newtypes.rst:11
msgid ""
"This section aims to give a quick fly-by on the various type methods you can "
"implement and what they do."
msgstr ""

#: extending/newtypes.rst:14
msgid ""
"Here is the definition of :c:type:`PyTypeObject`, with some fields only used "
"in debug builds omitted:"
msgstr ""

#: extending/newtypes.rst:20
msgid ""
"Now that's a *lot* of methods.  Don't worry too much though -- if you have a "
"type you want to define, the chances are very good that you will only "
"implement a handful of these."
msgstr ""

#: extending/newtypes.rst:24
msgid ""
"As you probably expect by now, we're going to go over this and give more "
"information about the various handlers.  We won't go in the order they are "
"defined in the structure, because there is a lot of historical baggage that "
"impacts the ordering of the fields.  It's often easiest to find an example "
"that includes the fields you need and then change the values to suit your "
"new type. ::"
msgstr ""

#: extending/newtypes.rst:33
msgid ""
"The name of the type -- as mentioned in the previous chapter, this will "
"appear in various places, almost entirely for diagnostic purposes. Try to "
"choose something that will be helpful in such a situation! ::"
msgstr ""

#: extending/newtypes.rst:39
msgid ""
"These fields tell the runtime how much memory to allocate when new objects "
"of this type are created.  Python has some built-in support for variable "
"length structures (think: strings, tuples) which is where the :c:member:"
"`~PyTypeObject.tp_itemsize` field comes in.  This will be dealt with "
"later. ::"
msgstr ""

#: extending/newtypes.rst:46
msgid ""
"Here you can put a string (or its address) that you want returned when the "
"Python script references ``obj.__doc__`` to retrieve the doc string."
msgstr ""

#: extending/newtypes.rst:49
msgid ""
"Now we come to the basic type methods -- the ones most extension types will "
"implement."
msgstr ""

#: extending/newtypes.rst:54
msgid "Finalization and De-allocation"
msgstr ""

#: extending/newtypes.rst:66
msgid ""
"This function is called when the reference count of the instance of your "
"type is reduced to zero and the Python interpreter wants to reclaim it.  If "
"your type has memory to free or other clean-up to perform, you can put it "
"here.  The object itself needs to be freed here as well.  Here is an example "
"of this function::"
msgstr ""

#: extending/newtypes.rst:83
msgid ""
"One important requirement of the deallocator function is that it leaves any "
"pending exceptions alone.  This is important since deallocators are "
"frequently called as the interpreter unwinds the Python stack; when the "
"stack is unwound due to an exception (rather than normal returns), nothing "
"is done to protect the deallocators from seeing that an exception has "
"already been set.  Any actions which a deallocator performs which may cause "
"additional Python code to be executed may detect that an exception has been "
"set.  This can lead to misleading errors from the interpreter.  The proper "
"way to protect against this is to save a pending exception before performing "
"the unsafe action, and restoring it when done.  This can be done using the :"
"c:func:`PyErr_Fetch` and :c:func:`PyErr_Restore` functions::"
msgstr ""

#: extending/newtypes.rst:122
msgid ""
"There are limitations to what you can safely do in a deallocator function. "
"First, if your type supports garbage collection (using :c:member:"
"`~PyTypeObject.tp_traverse` and/or :c:member:`~PyTypeObject.tp_clear`), some "
"of the object's members can have been cleared or finalized by the time :c:"
"member:`~PyTypeObject.tp_dealloc` is called.  Second, in :c:member:"
"`~PyTypeObject.tp_dealloc`, your object is in an unstable state: its "
"reference count is equal to zero.  Any call to a non-trivial object or API "
"(as in the example above) might end up calling :c:member:`~PyTypeObject."
"tp_dealloc` again, causing a double free and a crash."
msgstr ""

#: extending/newtypes.rst:131
msgid ""
"Starting with Python 3.4, it is recommended not to put any complex "
"finalization code in :c:member:`~PyTypeObject.tp_dealloc`, and instead use "
"the new :c:member:`~PyTypeObject.tp_finalize` type method."
msgstr ""

#: extending/newtypes.rst:136
msgid ":pep:`442` explains the new finalization scheme."
msgstr ""

#: extending/newtypes.rst:143
msgid "Object Presentation"
msgstr ""

#: extending/newtypes.rst:145
msgid ""
"In Python, there are two ways to generate a textual representation of an "
"object: the :func:`repr` function, and the :func:`str` function.  (The :func:"
"`print` function just calls :func:`str`.)  These handlers are both optional."
msgstr ""

#: extending/newtypes.rst:154
msgid ""
"The :c:member:`~PyTypeObject.tp_repr` handler should return a string object "
"containing a representation of the instance for which it is called.  Here is "
"a simple example::"
msgstr ""

#: extending/newtypes.rst:165
msgid ""
"If no :c:member:`~PyTypeObject.tp_repr` handler is specified, the "
"interpreter will supply a representation that uses the type's :c:member:"
"`~PyTypeObject.tp_name` and a uniquely-identifying value for the object."
msgstr ""

#: extending/newtypes.rst:169
msgid ""
"The :c:member:`~PyTypeObject.tp_str` handler is to :func:`str` what the :c:"
"member:`~PyTypeObject.tp_repr` handler described above is to :func:`repr`; "
"that is, it is called when Python code calls :func:`str` on an instance of "
"your object.  Its implementation is very similar to the :c:member:"
"`~PyTypeObject.tp_repr` function, but the resulting string is intended for "
"human consumption.  If :c:member:`~PyTypeObject.tp_str` is not specified, "
"the :c:member:`~PyTypeObject.tp_repr` handler is used instead."
msgstr ""

#: extending/newtypes.rst:176
msgid "Here is a simple example::"
msgstr ""

#: extending/newtypes.rst:188
msgid "Attribute Management"
msgstr ""

#: extending/newtypes.rst:190
msgid ""
"For every object which can support attributes, the corresponding type must "
"provide the functions that control how the attributes are resolved.  There "
"needs to be a function which can retrieve attributes (if any are defined), "
"and another to set attributes (if setting attributes is allowed).  Removing "
"an attribute is a special case, for which the new value passed to the "
"handler is ``NULL``."
msgstr ""

#: extending/newtypes.rst:196
msgid ""
"Python supports two pairs of attribute handlers; a type that supports "
"attributes only needs to implement the functions for one pair.  The "
"difference is that one pair takes the name of the attribute as a :c:type:"
"`char\\*`, while the other accepts a :c:type:`PyObject\\*`.  Each type can "
"use whichever pair makes more sense for the implementation's convenience. ::"
msgstr ""

#: extending/newtypes.rst:208
msgid ""
"If accessing attributes of an object is always a simple operation (this will "
"be explained shortly), there are generic implementations which can be used "
"to provide the :c:type:`PyObject\\*` version of the attribute management "
"functions. The actual need for type-specific attribute handlers almost "
"completely disappeared starting with Python 2.2, though there are many "
"examples which have not been updated to use some of the new generic "
"mechanism that is available."
msgstr ""

#: extending/newtypes.rst:219
msgid "Generic Attribute Management"
msgstr ""

#: extending/newtypes.rst:221
msgid ""
"Most extension types only use *simple* attributes.  So, what makes the "
"attributes simple?  There are only a couple of conditions that must be met:"
msgstr ""

#: extending/newtypes.rst:224
msgid ""
"The name of the attributes must be known when :c:func:`PyType_Ready` is "
"called."
msgstr ""

#: extending/newtypes.rst:227
msgid ""
"No special processing is needed to record that an attribute was looked up or "
"set, nor do actions need to be taken based on the value."
msgstr ""

#: extending/newtypes.rst:230
msgid ""
"Note that this list does not place any restrictions on the values of the "
"attributes, when the values are computed, or how relevant data is stored."
msgstr ""

#: extending/newtypes.rst:233
msgid ""
"When :c:func:`PyType_Ready` is called, it uses three tables referenced by "
"the type object to create :term:`descriptor`\\s which are placed in the "
"dictionary of the type object.  Each descriptor controls access to one "
"attribute of the instance object.  Each of the tables is optional; if all "
"three are ``NULL``, instances of the type will only have attributes that are "
"inherited from their base type, and should leave the :c:member:"
"`~PyTypeObject.tp_getattro` and :c:member:`~PyTypeObject.tp_setattro` fields "
"``NULL`` as well, allowing the base type to handle attributes."
msgstr ""

#: extending/newtypes.rst:241
msgid "The tables are declared as three fields of the type object::"
msgstr ""

#: extending/newtypes.rst:247
msgid ""
"If :c:member:`~PyTypeObject.tp_methods` is not ``NULL``, it must refer to an "
"array of :c:type:`PyMethodDef` structures.  Each entry in the table is an "
"instance of this structure::"
msgstr ""

#: extending/newtypes.rst:258
msgid ""
"One entry should be defined for each method provided by the type; no entries "
"are needed for methods inherited from a base type.  One additional entry is "
"needed at the end; it is a sentinel that marks the end of the array.  The :"
"attr:`ml_name` field of the sentinel must be ``NULL``."
msgstr ""

#: extending/newtypes.rst:263
msgid ""
"The second table is used to define attributes which map directly to data "
"stored in the instance.  A variety of primitive C types are supported, and "
"access may be read-only or read-write.  The structures in the table are "
"defined as::"
msgstr ""

#: extending/newtypes.rst:275
msgid ""
"For each entry in the table, a :term:`descriptor` will be constructed and "
"added to the type which will be able to extract a value from the instance "
"structure.  The :attr:`type` field should contain one of the type codes "
"defined in the :file:`structmember.h` header; the value will be used to "
"determine how to convert Python values to and from C values.  The :attr:"
"`flags` field is used to store flags which control how the attribute can be "
"accessed."
msgstr ""

#: extending/newtypes.rst:282
msgid ""
"The following flag constants are defined in :file:`structmember.h`; they may "
"be combined using bitwise-OR."
msgstr ""

#: extending/newtypes.rst:286
msgid "Constant"
msgstr "Constante"

#: extending/newtypes.rst:286
msgid "Meaning"
msgstr "Signification"

#: extending/newtypes.rst:288
msgid ":const:`READONLY`"
msgstr ""

#: extending/newtypes.rst:288
msgid "Never writable."
msgstr ""

#: extending/newtypes.rst:290
msgid ":const:`READ_RESTRICTED`"
msgstr ""

#: extending/newtypes.rst:290
msgid "Not readable in restricted mode."
msgstr ""

#: extending/newtypes.rst:292
msgid ":const:`WRITE_RESTRICTED`"
msgstr ""

#: extending/newtypes.rst:292
msgid "Not writable in restricted mode."
msgstr ""

#: extending/newtypes.rst:294
msgid ":const:`RESTRICTED`"
msgstr ""

#: extending/newtypes.rst:294
msgid "Not readable or writable in restricted mode."
msgstr ""

#: extending/newtypes.rst:303
msgid ""
"An interesting advantage of using the :c:member:`~PyTypeObject.tp_members` "
"table to build descriptors that are used at runtime is that any attribute "
"defined this way can have an associated doc string simply by providing the "
"text in the table.  An application can use the introspection API to retrieve "
"the descriptor from the class object, and get the doc string using its :attr:"
"`__doc__` attribute."
msgstr ""

#: extending/newtypes.rst:309
msgid ""
"As with the :c:member:`~PyTypeObject.tp_methods` table, a sentinel entry "
"with a :attr:`name` value of ``NULL`` is required."
msgstr ""

#: extending/newtypes.rst:323
msgid "Type-specific Attribute Management"
msgstr ""

#: extending/newtypes.rst:325
msgid ""
"For simplicity, only the :c:type:`char\\*` version will be demonstrated "
"here; the type of the name parameter is the only difference between the :c:"
"type:`char\\*` and :c:type:`PyObject\\*` flavors of the interface. This "
"example effectively does the same thing as the generic example above, but "
"does not use the generic support added in Python 2.2.  It explains how the "
"handler functions are called, so that if you do need to extend their "
"functionality, you'll understand what needs to be done."
msgstr ""

#: extending/newtypes.rst:333
msgid ""
"The :c:member:`~PyTypeObject.tp_getattr` handler is called when the object "
"requires an attribute look-up.  It is called in the same situations where "
"the :meth:`__getattr__` method of a class would be called."
msgstr ""

#: extending/newtypes.rst:337
msgid "Here is an example::"
msgstr "Voici un exemple ::"

#: extending/newtypes.rst:353
msgid ""
"The :c:member:`~PyTypeObject.tp_setattr` handler is called when the :meth:"
"`__setattr__` or :meth:`__delattr__` method of a class instance would be "
"called.  When an attribute should be deleted, the third parameter will be "
"``NULL``.  Here is an example that simply raises an exception; if this were "
"really all you wanted, the :c:member:`~PyTypeObject.tp_setattr` handler "
"should be set to ``NULL``. ::"
msgstr ""

#: extending/newtypes.rst:367
msgid "Object Comparison"
msgstr ""

#: extending/newtypes.rst:373
msgid ""
"The :c:member:`~PyTypeObject.tp_richcompare` handler is called when "
"comparisons are needed.  It is analogous to the :ref:`rich comparison "
"methods <richcmpfuncs>`, like :meth:`__lt__`, and also called by :c:func:"
"`PyObject_RichCompare` and :c:func:`PyObject_RichCompareBool`."
msgstr ""

#: extending/newtypes.rst:378
msgid ""
"This function is called with two Python objects and the operator as "
"arguments, where the operator is one of ``Py_EQ``, ``Py_NE``, ``Py_LE``, "
"``Py_GT``, ``Py_LT`` or ``Py_GT``.  It should compare the two objects with "
"respect to the specified operator and return ``Py_True`` or ``Py_False`` if "
"the comparison is successful, ``Py_NotImplemented`` to indicate that "
"comparison is not implemented and the other object's comparison method "
"should be tried, or ``NULL`` if an exception was set."
msgstr ""

#: extending/newtypes.rst:386
msgid ""
"Here is a sample implementation, for a datatype that is considered equal if "
"the size of an internal pointer is equal::"
msgstr ""

#: extending/newtypes.rst:416
msgid "Abstract Protocol Support"
msgstr ""

#: extending/newtypes.rst:418
msgid ""
"Python supports a variety of *abstract* 'protocols;' the specific interfaces "
"provided to use these interfaces are documented in :ref:`abstract`."
msgstr ""

#: extending/newtypes.rst:422
msgid ""
"A number of these abstract interfaces were defined early in the development "
"of the Python implementation.  In particular, the number, mapping, and "
"sequence protocols have been part of Python since the beginning.  Other "
"protocols have been added over time.  For protocols which depend on several "
"handler routines from the type implementation, the older protocols have been "
"defined as optional blocks of handlers referenced by the type object.  For "
"newer protocols there are additional slots in the main type object, with a "
"flag bit being set to indicate that the slots are present and should be "
"checked by the interpreter.  (The flag bit does not indicate that the slot "
"values are non-``NULL``. The flag may be set to indicate the presence of a "
"slot, but a slot may still be unfilled.) ::"
msgstr ""

#: extending/newtypes.rst:437
msgid ""
"If you wish your object to be able to act like a number, a sequence, or a "
"mapping object, then you place the address of a structure that implements "
"the C type :c:type:`PyNumberMethods`, :c:type:`PySequenceMethods`, or :c:"
"type:`PyMappingMethods`, respectively. It is up to you to fill in this "
"structure with appropriate values. You can find examples of the use of each "
"of these in the :file:`Objects` directory of the Python source "
"distribution. ::"
msgstr ""

#: extending/newtypes.rst:446
msgid ""
"This function, if you choose to provide it, should return a hash number for "
"an instance of your data type. Here is a simple example::"
msgstr ""

#: extending/newtypes.rst:459
msgid ""
":c:type:`Py_hash_t` is a signed integer type with a platform-varying width. "
"Returning ``-1`` from :c:member:`~PyTypeObject.tp_hash` indicates an error, "
"which is why you should be careful to avoid returning it when hash "
"computation is successful, as seen above."
msgstr ""

#: extending/newtypes.rst:468
msgid ""
"This function is called when an instance of your data type is \"called\", "
"for example, if ``obj1`` is an instance of your data type and the Python "
"script contains ``obj1('hello')``, the :c:member:`~PyTypeObject.tp_call` "
"handler is invoked."
msgstr ""

#: extending/newtypes.rst:472
msgid "This function takes three arguments:"
msgstr ""

#: extending/newtypes.rst:474
msgid ""
"*self* is the instance of the data type which is the subject of the call. If "
"the call is ``obj1('hello')``, then *self* is ``obj1``."
msgstr ""

#: extending/newtypes.rst:477
msgid ""
"*args* is a tuple containing the arguments to the call.  You can use :c:func:"
"`PyArg_ParseTuple` to extract the arguments."
msgstr ""

#: extending/newtypes.rst:480
msgid ""
"*kwds* is a dictionary of keyword arguments that were passed. If this is non-"
"``NULL`` and you support keyword arguments, use :c:func:"
"`PyArg_ParseTupleAndKeywords` to extract the arguments.  If you do not want "
"to support keyword arguments and this is non-``NULL``, raise a :exc:"
"`TypeError` with a message saying that keyword arguments are not supported."
msgstr ""

#: extending/newtypes.rst:486
msgid "Here is a toy ``tp_call`` implementation::"
msgstr ""

#: extending/newtypes.rst:512
msgid ""
"These functions provide support for the iterator protocol.  Both handlers "
"take exactly one parameter, the instance for which they are being called, "
"and return a new reference.  In the case of an error, they should set an "
"exception and return ``NULL``.  :c:member:`~PyTypeObject.tp_iter` "
"corresponds to the Python :meth:`__iter__` method, while :c:member:"
"`~PyTypeObject.tp_iternext` corresponds to the Python :meth:`~iterator."
"__next__` method."
msgstr ""

#: extending/newtypes.rst:519
msgid ""
"Any :term:`iterable` object must implement the :c:member:`~PyTypeObject."
"tp_iter` handler, which must return an :term:`iterator` object.  Here the "
"same guidelines apply as for Python classes:"
msgstr ""

#: extending/newtypes.rst:523
msgid ""
"For collections (such as lists and tuples) which can support multiple "
"independent iterators, a new iterator should be created and returned by each "
"call to :c:member:`~PyTypeObject.tp_iter`."
msgstr ""

#: extending/newtypes.rst:526
msgid ""
"Objects which can only be iterated over once (usually due to side effects of "
"iteration, such as file objects) can implement :c:member:`~PyTypeObject."
"tp_iter` by returning a new reference to themselves -- and should also "
"therefore implement the :c:member:`~PyTypeObject.tp_iternext`  handler."
msgstr ""

#: extending/newtypes.rst:531
msgid ""
"Any :term:`iterator` object should implement both :c:member:`~PyTypeObject."
"tp_iter` and :c:member:`~PyTypeObject.tp_iternext`.  An iterator's :c:member:"
"`~PyTypeObject.tp_iter` handler should return a new reference to the "
"iterator.  Its :c:member:`~PyTypeObject.tp_iternext` handler should return a "
"new reference to the next object in the iteration, if there is one. If the "
"iteration has reached the end, :c:member:`~PyTypeObject.tp_iternext` may "
"return ``NULL`` without setting an exception, or it may set :exc:"
"`StopIteration` *in addition* to returning ``NULL``; avoiding the exception "
"can yield slightly better performance.  If an actual error occurs, :c:member:"
"`~PyTypeObject.tp_iternext` should always set an exception and return "
"``NULL``."
msgstr ""

#: extending/newtypes.rst:547
msgid "Weak Reference Support"
msgstr ""

#: extending/newtypes.rst:549
msgid ""
"One of the goals of Python's weak reference implementation is to allow any "
"type to participate in the weak reference mechanism without incurring the "
"overhead on performance-critical objects (such as numbers)."
msgstr ""

#: extending/newtypes.rst:554
msgid "Documentation for the :mod:`weakref` module."
msgstr ""

#: extending/newtypes.rst:556
msgid ""
"For an object to be weakly referencable, the extension type must do two "
"things:"
msgstr ""

#: extending/newtypes.rst:558
msgid ""
"Include a :c:type:`PyObject\\*` field in the C object structure dedicated to "
"the weak reference mechanism.  The object's constructor should leave it "
"``NULL`` (which is automatic when using the default :c:member:`~PyTypeObject."
"tp_alloc`)."
msgstr ""

#: extending/newtypes.rst:563
msgid ""
"Set the :c:member:`~PyTypeObject.tp_weaklistoffset` type member to the "
"offset of the aforementioned field in the C object structure, so that the "
"interpreter knows how to access and modify that field."
msgstr ""

#: extending/newtypes.rst:567
msgid ""
"Concretely, here is how a trivial object structure would be augmented with "
"the required field::"
msgstr ""

#: extending/newtypes.rst:575
msgid "And the corresponding member in the statically-declared type object::"
msgstr ""

#: extending/newtypes.rst:583
msgid ""
"The only further addition is that ``tp_dealloc`` needs to clear any weak "
"references (by calling :c:func:`PyObject_ClearWeakRefs`) if the field is non-"
"``NULL``::"
msgstr ""

#: extending/newtypes.rst:599
msgid "More Suggestions"
msgstr ""

#: extending/newtypes.rst:601
msgid ""
"In order to learn how to implement any specific method for your new data "
"type, get the :term:`CPython` source code.  Go to the :file:`Objects` "
"directory, then search the C source files for ``tp_`` plus the function you "
"want (for example, ``tp_richcompare``).  You will find examples of the "
"function you want to implement."
msgstr ""

#: extending/newtypes.rst:607
msgid ""
"When you need to verify that an object is a concrete instance of the type "
"you are implementing, use the :c:func:`PyObject_TypeCheck` function.  A "
"sample of its use might be something like the following::"
msgstr ""

#: extending/newtypes.rst:618
msgid "Download CPython source releases."
msgstr ""

#: extending/newtypes.rst:618
msgid "https://www.python.org/downloads/source/"
msgstr ""

#: extending/newtypes.rst:620
msgid ""
"The CPython project on GitHub, where the CPython source code is developed."
msgstr ""

#: extending/newtypes.rst:621
msgid "https://github.com/python/cpython"
msgstr ""