# Analyse des arguments et construction des valeurs

Ces fonctions sont utiles pour créer vos propres fonctions et méthodes d'extensions. Des informations supplémentaires et des exemples sont disponibles ici: Extension et intégration de l'interpréteur Python.

Dans Les trois premières de ces fonctions décrites, `PyArg_ParseTuple()`, `PyArg_ParseTupleAndKeywords()`, et `PyArg_Parse()`, toutes utilisent des chaînes de format qui sont utilisées pour indiquer à la fonction les arguments attendus. Les chaînes de format utilise la même syntaxe pour chacune de ces fonctions.

## Analyse des arguments

Une chaîne de format se compose de zéro ou plusieurs "unités de format". Une unité de format décrit un objet Python, elle est généralement composée d'un seul caractère ou d'une séquence d'unités de format entre parenthèses. À quelques exceptions près, une unité de format qui n'est pas une séquence entre parenthèses correspond normalement à un argument d'une seule adresse pour ces fonctions. Dans la description qui suit, la forme entre guillemets est l'unité de format, l'entrée entre parenthèses est le type d'objet Python qui correspond à l'unité de format, et l'entrée entre crochets est le type de la variable C (ou des variables) dont l'adresse doit être donnée.

### Chaînes et tampons

Ces formats permettent d'accéder à un objet sous forme d'un fragment de mémoire contiguë. Il n'est pas nécessaire d'allouer la mémoire pour l'unicode ou le bytes renvoyé.

Sauf indication contraire, les tampons ne se terminent pas par NUL.

There are three ways strings and buffers can be converted to C:

- Formats such as `y*` and `s*` fill a `Py_buffer` structure. This locks the underlying buffer so that the caller can subsequently use the buffer even inside a `Py_BEGIN_ALLOW_THREADS` block without the risk of mutable data being resized or destroyed. As a result, you have to call `PyBuffer_Release()` after you have finished processing the data (or in any early abort case).

- The `es`, `es#`, `et` and `et#` formats allocate the result buffer. You have to call `PyMem_Free()` after you have finished processing the data (or in any early abort case).

- Other formats take a `str` or a read-only bytes-like object, such as `bytes`, and provide a `const char *` pointer to its buffer. In this case the buffer is "borrowed": it is managed by the corresponding Python object, and shares the lifetime of this object. You won't have to release any memory yourself.

  To ensure that the underlying buffer may be safely borrowed, the object's `PyBufferProcs.bf_releasebuffer` field must be `NULL`. This disallows common mutable objects such as `bytearray`, but also some read-only objects such as `memoryview` of `bytes`.

  Besides this `bf_releasebuffer` requirement, there is no check to verify whether the input object is immutable (e.g. whether it would honor a request for a writable buffer, or whether another thread can mutate the data).

Note

For all `#` variants of formats (`s#`, `y#`, etc.), the macro `PY_SSIZE_T_CLEAN` must be defined before including `Python.h`. On Python 3.9 and older, the type of the length argument is `Py_ssize_t` if the `PY_SSIZE_T_CLEAN` macro is defined, or int otherwise.

`s` (`str`) [`const char *`]

  Convertit un objet Unicode en un pointeur vers une chaîne de caractères. S'il s'agit d'un pointeur vers une chaîne de caractères déjà existante, il est stocké dans la variable de type pointeur vers un caractère dont vous avez donné l'adresse. Une chaîne de caractères en C se termine par NULL. La chaîne de caractères Python ne doit donc pas contenir de caractère dont le code est null. Si elle en contient, une exception `ValueError` est levée. Si la conversion échoue, une `UnicodeError` est levée.

  Note

  Ce format n'accepte pas les objets compatibles avec une chaîne d'octets. Si vous voulez accepter les chemins du système de fichiers et les convertir vers des chaînes de caractères C, il est préférable d'utiliser le format `O&` avec `PyUnicode_FSConverter()` en tant que converter.

  Modifié dans la version 3.5: Auparavant, une `TypeError` était levée quand la chaîne de caractères Python contenait des codes NULL.

`s*` (`str` ou bytes-like object) [`Py_buffer`]

  Ce format accepte les objets Unicode et les bytes-like object. Cela remplit une structure `Py_buffer` qui est fournie par l'appelant. Dans ce cas, la chaîne de caractères C qui en résulte peut contenir des octets NULL. Les objets Unicode sont convertis en chaînes de caractères C en utilisant l'encodage `'utf-8'`.

`s#` (`str`, read-only bytes-like object) [const char *, `Py_ssize_t`]

  Like `s*`, except that it provides a borrowed buffer. The result is stored into two C variables, the first one a pointer to a C string, the second one its length. The string may contain embedded null bytes. Unicode objects are converted to C strings using `'utf-8'` encoding.

`z` (`str` ou `None`) [`const char *`]

  Like `s`, but the Python object may also be `None`, in which case the C pointer is set to `NULL`.

`z*` (`str`, bytes-like object ou `None`) [`Py_buffer`]

  Comme `s*`, mais l'objet Python peut aussi être `None`, auquel cas le membre `buf`, dont la structure est `Py_buffer` est fixée à NULL.

`z#` (`str`, read-only bytes-like object or `None`) [const char *, `Py_ssize_t`]

  Like `s#`, but the Python object may also be `None`, in which case the C pointer is set to `NULL`.

`y` (lecture seule objet compatible avec une chaîne d'octets) [constante char *]

  This format converts a bytes-like object to a C pointer to a borrowed character string; it does not accept Unicode objects. The bytes buffer must not contain embedded null bytes; if it does, a `ValueError` exception is raised.

  Modifié dans la version 3.5: Auparavant, `TypeError` était levée lorsque des octets null étaient rencontrés dans le tampon d'octets.

`y*` (bytes-like object) [`Py_buffer`]

  This variant on `s*` doesn't accept Unicode objects, only bytes-like objects. This is the recommended way to accept binary data.

`y#` (read-only bytes-like object) [const char *, `Py_ssize_t`]

  Cette variante de `s#` n'accepte pas les objets Unicode, uniquement des objets assimilés à des octets.

`S` (`bytes`) [`PyBytesObject *`]

  Requires that the Python object is a `bytes` object, without attempting any conversion. Raises `TypeError` if the object is not a bytes object. The C variable may also be declared as PyObject*.

`Y` (`bytearray`) [`PyByteArrayObject *`]

  Requires that the Python object is a `bytearray` object, without attempting any conversion. Raises `TypeError` if the object is not a `bytearray` object. The C variable may also be declared as PyObject*.

`U` (`str`) [`PyObject *`]

  Requires that the Python object is a Unicode object, without attempting any conversion. Raises `TypeError` if the object is not a Unicode object. The C variable may also be declared as PyObject*.

`w*` (lecture-écriture bytes-like object) [`Py_buffer`]

  This format accepts any object which implements the read-write buffer interface. It fills a `Py_buffer` structure provided by the caller. The buffer may contain embedded null bytes. The caller have to call `PyBuffer_Release()` when it is done with the buffer.

`es` (`str`) [const char *encoding, char **buffer]

  This variant on `s` is used for encoding Unicode into a character buffer. It only works for encoded data without embedded NUL bytes.

  This format requires two arguments. The first is only used as input, and must be a const char* which points to the name of an encoding as a NUL-terminated string, or `NULL`, in which case `'utf-8'` encoding is used. An exception is raised if the named encoding is not known to Python. The second argument must be a char**; the value of the pointer it references will be set to a buffer with the contents of the argument text. The text will be encoded in the encoding specified by the first argument.

  `PyArg_ParseTuple()` will allocate a buffer of the needed size, copy the encoded data into this buffer and adjust *buffer to reference the newly allocated storage. The caller is responsible for calling `PyMem_Free()` to free the allocated buffer after use.

`et` (`str`, `bytes` or `bytearray`) [const char *encoding, char **buffer]

  Same as `es` except that byte string objects are passed through without recoding them. Instead, the implementation assumes that the byte string object uses the encoding passed in as parameter.

`es#` (`str`) [const char *encoding, char **buffer, `Py_ssize_t` *buffer_length]

  This variant on `s#` is used for encoding Unicode into a character buffer. Unlike the `es` format, this variant allows input data which contains NUL characters.

  It requires three arguments. The first is only used as input, and must be a const char* which points to the name of an encoding as a NUL-terminated string, or `NULL`, in which case `'utf-8'` encoding is used. An exception is raised if the named encoding is not known to Python. The second argument must be a char**; the value of the pointer it references will be set to a buffer with the contents of the argument text. The text will be encoded in the encoding specified by the first argument. The third argument must be a pointer to an integer; the referenced integer will be set to the number of bytes in the output buffer.

  Il existe deux modes de fonctionnement :

  If *buffer points a `NULL` pointer, the function will allocate a buffer of the needed size, copy the encoded data into this buffer and set *buffer to reference the newly allocated storage. The caller is responsible for calling `PyMem_Free()` to free the allocated buffer after usage.

  If *buffer points to a non-`NULL` pointer (an already allocated buffer), `PyArg_ParseTuple()` will use this location as the buffer and interpret the initial value of *buffer_length as the buffer size. It will then copy the encoded data into the buffer and NUL-terminate it. If the buffer is not large enough, a `ValueError` will be set.

  Dans les deux cas, *buffer_length est la longueur des données encodées, sans l'octet NUL de fin.

`et#` (`str`, `bytes` or `bytearray`) [const char *encoding, char **buffer, `Py_ssize_t` *buffer_length]

  Same as `es#` except that byte string objects are passed through without recoding them. Instead, the implementation assumes that the byte string object uses the encoding passed in as parameter.

Modifié dans la version 3.12: `u`, `u#`, `Z`, and `Z#` are removed because they used a legacy `Py_UNICODE*` representation.

### Les nombres

`b` (`int`) [`unsigned char`]

  Convert a nonnegative Python integer to an unsigned tiny int, stored in a C unsigned char.

`B` (`int`) [`unsigned char`]

  Convert a Python integer to a tiny int without overflow checking, stored in a C unsigned char.

`h` (`int`) [`short int`]

  Convert a Python integer to a C short int.

`H` (`int`) [`unsigned short int`]

  Convert a Python integer to a C unsigned short int, without overflow checking.

`i` (`int`) [`int`]

  Convert a Python integer to a plain C int.

`I` (`int`) [`unsigned int`]

  Convert a Python integer to a C unsigned int, without overflow checking.

`l` (`int`) [`long int`]

  Convert a Python integer to a C long int.

`k` (`int`) [`unsigned long`]

  Convert a Python integer to a C unsigned long without overflow checking.

`L` (`int`) [`long long`]

  Convert a Python integer to a C long long.

`K` (`int`) [`unsigned long long`]

  Convert a Python integer to a C unsigned long long without overflow checking.

`n` (`int`) [`Py_ssize_t`]

  Convertit un entier Python en un `Py_ssize_t`.

`c` (`bytes` ou `bytearray` de longueur 1) [`char`]

  Convert a Python byte, represented as a `bytes` or `bytearray` object of length 1, to a C char.

  Modifié dans la version 3.3: Allow `bytearray` objects.

`C` (`str` de longueur 1) [`int`]

  Convert a Python character, represented as a `str` object of length 1, to a C int.

`f` (`float`) [`float`]

  Convert a Python floating-point number to a C float.

`d` (`float`) [`double`]

  Convert a Python floating-point number to a C double.

`D` (`complex`) [`Py_complex`]

  Convertit un nombre complexe Python vers une structure `Py_complex` C.

### Autres objets

`O` (objet) [`PyObject *`]

  Store a Python object (without any conversion) in a C object pointer. The C program thus receives the actual object that was passed. A new strong reference to the object is not created (i.e. its reference count is not increased). The pointer stored is not `NULL`.

`O!` (objet) [typeobject, `PyObject *`]

  Store a Python object in a C object pointer. This is similar to `O`, but takes two C arguments: the first is the address of a Python type object, the second is the address of the C variable (of type PyObject*) into which the object pointer is stored. If the Python object does not have the required type, `TypeError` is raised.

`O&` (objet) [converter, anything]

  Convert a Python object to a C variable through a converter function. This takes two arguments: the first is a function, the second is the address of a C variable (of arbitrary type), converted to void*. The converter function in turn is called as follows:

      status = converter(object, address);

  where object is the Python object to be converted and address is the void* argument that was passed to the `PyArg_Parse*` function. The returned status should be `1` for a successful conversion and `0` if the conversion has failed. When the conversion fails, the converter function should raise an exception and leave the content of address unmodified.

  If the converter returns `Py_CLEANUP_SUPPORTED`, it may get called a second time if the argument parsing eventually fails, giving the converter a chance to release any memory that it had already allocated. In this second call, the object parameter will be `NULL`; address will have the same value as in the original call.

  Modifié dans la version 3.1: `Py_CLEANUP_SUPPORTED` à été ajouté.

`p` (`bool`) [`int`]

  Tests the value passed in for truth (a boolean predicate) and converts the result to its equivalent C true/false integer value. Sets the int to `1` if the expression was true and `0` if it was false. This accepts any valid Python value. See Valeurs booléennes for more information about how Python tests values for truth.

  Ajouté dans la version 3.3.

`(items)` (`tuple`) [matching-items]

  L'objet doit être une séquence Python dont la longueur est le nombre d'unités de formats dans articles. Les arguments C doivent correspondre à chaque unité de format particulière dans articles. Les unités de formats pour les séquences peuvent être imbriquées.

It is possible to pass "long" integers (integers whose value exceeds the platform's `LONG_MAX`) however no proper range checking is done --- the most significant bits are silently truncated when the receiving field is too small to receive the value (actually, the semantics are inherited from downcasts in C --- your mileage may vary).

Quelques autres caractères ont un sens dans une chaîne de format. On ne doit pas les trouvées dans des parenthèses imbriquées. Ce sont :

`|`

  Indicates that the remaining arguments in the Python argument list are optional. The C variables corresponding to optional arguments should be initialized to their default value --- when an optional argument is not specified, `PyArg_ParseTuple()` does not touch the contents of the corresponding C variable(s).

`$`

  `PyArg_ParseTupleAndKeywords()` only: Indicates that the remaining arguments in the Python argument list are keyword-only. Currently, all keyword-only arguments must also be optional arguments, so `|` must always be specified before `$` in the format string.

  Ajouté dans la version 3.3.

`:`

  The list of format units ends here; the string after the colon is used as the function name in error messages (the "associated value" of the exception that `PyArg_ParseTuple()` raises).

`;`

  La liste des unités de format s'arrête ici ; la chaîne après le point-virgule est utilise comme message d'erreur au lieu du message d'erreur par défaut. `:` et `;` sont mutuellement exclusifs.

Note that any Python object references which are provided to the caller are borrowed references; do not release them (i.e. do not decrement their reference count)!

Les arguments additionnels qui sont donnés à ces fonctions doivent être des adresses de variables dont le type est déterminé par la chaîne de format. Elles sont utilisées pour stocker les valeurs du n-uplet d'entrée. Il y a quelques cas, comme décrit précédemment dans le liste des unités de formats, où ces paramètres sont utilisés comme valeurs d'entrée. Dans ce cas, ils devraient correspondre à ce qui est spécifié pour l'unité de format correspondante.

For the conversion to succeed, the arg object must match the format and the format must be exhausted. On success, the `PyArg_Parse*` functions return true, otherwise they return false and raise an appropriate exception. When the `PyArg_Parse*` functions fail due to conversion failure in one of the format units, the variables at the addresses corresponding to that and the following format units are left untouched.

### Fonction de l'API

int PyArg_ParseTuple(PyObject *args, const char *format, ...)
  Part of the Stable ABI.

  Parse the parameters of a function that takes only positional parameters into local variables. Returns true on success; on failure, it returns false and raises the appropriate exception.

int PyArg_VaParse(PyObject *args, const char *format, va_list vargs)
  Part of the Stable ABI.

  Identical to `PyArg_ParseTuple()`, except that it accepts a va_list rather than a variable number of arguments.

int PyArg_ParseTupleAndKeywords(PyObject *args, PyObject *kw, const char *format, char *keywords[], ...)
  Part of the Stable ABI.

  Parse the parameters of a function that takes both positional and keyword parameters into local variables. The keywords argument is a `NULL`-terminated array of keyword parameter names. Empty names denote positional-only parameters. Returns true on success; on failure, it returns false and raises the appropriate exception.

  Modifié dans la version 3.6: Added support for positional-only parameters.

int PyArg_VaParseTupleAndKeywords(PyObject *args, PyObject *kw, const char *format, char *keywords[], va_list vargs)
  Part of the Stable ABI.

  Identical to `PyArg_ParseTupleAndKeywords()`, except that it accepts a va_list rather than a variable number of arguments.

int PyArg_ValidateKeywordArguments(PyObject*)
  Part of the Stable ABI.

  Ensure that the keys in the keywords argument dictionary are strings. This is only needed if `PyArg_ParseTupleAndKeywords()` is not used, since the latter already does this check.

  Ajouté dans la version 3.2.

int PyArg_Parse(PyObject *args, const char *format, ...)
  Part of the Stable ABI.

  Function used to deconstruct the argument lists of "old-style" functions --- these are functions which use the `METH_OLDARGS` parameter parsing method, which has been removed in Python 3. This is not recommended for use in parameter parsing in new code, and most code in the standard interpreter has been modified to no longer use this for that purpose. It does remain a convenient way to decompose other tuples, however, and may continue to be used for that purpose.

int PyArg_UnpackTuple(PyObject *args, const char *name, Py_ssize_t min, Py_ssize_t max, ...)
  Part of the Stable ABI.

  A simpler form of parameter retrieval which does not use a format string to specify the types of the arguments. Functions which use this method to retrieve their parameters should be declared as `METH_VARARGS` in function or method tables. The tuple containing the actual parameters should be passed as args; it must actually be a tuple. The length of the tuple must be at least min and no more than max; min and max may be equal. Additional arguments must be passed to the function, each of which should be a pointer to a PyObject* variable; these will be filled in with the values from args; they will contain borrowed references. The variables which correspond to optional parameters not given by args will not be filled in; these should be initialized by the caller. This function returns true on success and false if args is not a tuple or contains the wrong number of elements; an exception will be set if there was a failure.

  This is an example of the use of this function, taken from the sources for the `_weakref` helper module for weak references:

      static PyObject *
      weakref_ref(PyObject *self, PyObject *args)
      {
          PyObject *object;
          PyObject *callback = NULL;
          PyObject *result = NULL;

          if (PyArg_UnpackTuple(args, "ref", 1, 2, &object, &callback)) {
              result = PyWeakref_NewRef(object, callback);
          }
          return result;
      }

  The call to `PyArg_UnpackTuple()` in this example is entirely equivalent to this call to `PyArg_ParseTuple()`:

      PyArg_ParseTuple(args, "O|O:ref", &object, &callback)

## Construction des valeurs

PyObject *Py_BuildValue(const char *format, ...)
  Valeur de retour : nouvelle référence. Part of the Stable ABI.

  Create a new value based on a format string similar to those accepted by the `PyArg_Parse*` family of functions and a sequence of values. Returns the value or `NULL` in the case of an error; an exception will be raised if `NULL` is returned.

  `Py_BuildValue()` does not always build a tuple. It builds a tuple only if its format string contains two or more format units. If the format string is empty, it returns `None`; if it contains exactly one format unit, it returns whatever object is described by that format unit. To force it to return a tuple of size 0 or one, parenthesize the format string.

  When memory buffers are passed as parameters to supply data to build objects, as for the `s` and `s#` formats, the required data is copied. Buffers provided by the caller are never referenced by the objects created by `Py_BuildValue()`. In other words, if your code invokes `malloc()` and passes the allocated memory to `Py_BuildValue()`, your code is responsible for calling `free()` for that memory once `Py_BuildValue()` returns.

  In the following description, the quoted form is the format unit; the entry in (round) parentheses is the Python object type that the format unit will return; and the entry in [square] brackets is the type of the C value(s) to be passed.

  The characters space, tab, colon and comma are ignored in format strings (but not within format units such as `s#`). This can be used to make long format strings a tad more readable.

  `s` (`str` ou `None`) [`const char *`]

    Convert a null-terminated C string to a Python `str` object using `'utf-8'` encoding. If the C string pointer is `NULL`, `None` is used.

  `s#` (`str` or `None`) [const char *, `Py_ssize_t`]

    Convert a C string and its length to a Python `str` object using `'utf-8'` encoding. If the C string pointer is `NULL`, the length is ignored and `None` is returned.

  `y` (`bytes`) [`const char *`]

    This converts a C string to a Python `bytes` object. If the C string pointer is `NULL`, `None` is returned.

  `y#` (`bytes`) [const char *, `Py_ssize_t`]

    This converts a C string and its lengths to a Python object. If the C string pointer is `NULL`, `None` is returned.

  `z` (`str` ou `None`) [`const char *`]

    Same as `s`.

  `z#` (`str` or `None`) [const char *, `Py_ssize_t`]

    Same as `s#`.

  `u` (`str`) [`const wchar_t *`]

    Convert a null-terminated `wchar_t` buffer of Unicode (UTF-16 or UCS-4) data to a Python Unicode object. If the Unicode buffer pointer is `NULL`, `None` is returned.

  `u#` (`str`) [const wchar_t *, `Py_ssize_t`]

    Convert a Unicode (UTF-16 or UCS-4) data buffer and its length to a Python Unicode object. If the Unicode buffer pointer is `NULL`, the length is ignored and `None` is returned.

  `U` (`str` ou `None`) [`const char *`]

    Same as `s`.

  `U#` (`str` or `None`) [const char *, `Py_ssize_t`]

    Same as `s#`.

  `i` (`int`) [`int`]

    Convert a plain C int to a Python integer object.

  `b` (`int`) [`char`]

    Convert a plain C char to a Python integer object.

  `h` (`int`) [`short int`]

    Convert a plain C short int to a Python integer object.

  `l` (`int`) [`long int`]

    Convert a C long int to a Python integer object.

  `B` (`int`) [`unsigned char`]

    Convert a C unsigned char to a Python integer object.

  `H` (`int`) [`unsigned short int`]

    Convert a C unsigned short int to a Python integer object.

  `I` (`int`) [`unsigned int`]

    Convert a C unsigned int to a Python integer object.

  `k` (`int`) [`unsigned long`]

    Convert a C unsigned long to a Python integer object.

  `L` (`int`) [`long long`]

    Convert a C long long to a Python integer object.

  `K` (`int`) [`unsigned long long`]

    Convert a C unsigned long long to a Python integer object.

  `n` (`int`) [`Py_ssize_t`]

    Convert a C `Py_ssize_t` to a Python integer.

  `c` (`bytes` de taille 1) [`char`]

    Convert a C int representing a byte to a Python `bytes` object of length 1.

  `C` (`str` de longueur 1) [`int`]

    Convert a C int representing a character to Python `str` object of length 1.

  `d` (`float`) [`double`]

    Convert a C double to a Python floating-point number.

  `f` (`float`) [`float`]

    Convert a C float to a Python floating-point number.

  `D` (`complex`) [`Py_complex *`]

    Convert a C `Py_complex` structure to a Python complex number.

  `O` (objet) [`PyObject *`]

    Pass a Python object untouched but create a new strong reference to it (i.e. its reference count is incremented by one). If the object passed in is a `NULL` pointer, it is assumed that this was caused because the call producing the argument found an error and set an exception. Therefore, `Py_BuildValue()` will return `NULL` but won't raise an exception. If no exception has been raised yet, `SystemError` is set.

  `S` (objet) [`PyObject *`]

    Same as `O`.

  `N` (objet) [`PyObject *`]

    Same as `O`, except it doesn't create a new strong reference. Useful when the object is created by a call to an object constructor in the argument list.

  `O&` (objet) [converter, anything]

    Convert anything to a Python object through a converter function. The function is called with anything (which should be compatible with void*) as its argument and should return a "new" Python object, or `NULL` if an error occurred.

  `(items)` (`tuple`) [matching-items]

    Convert a sequence of C values to a Python tuple with the same number of items.

  `[items]` (`list`) [matching-items]

    Convert a sequence of C values to a Python list with the same number of items.

  `{items}` (`dict`) [matching-items]

    Convert a sequence of C values to a Python dictionary. Each pair of consecutive C values adds one item to the dictionary, serving as key and value, respectively.

  If there is an error in the format string, the `SystemError` exception is set and `NULL` returned.

PyObject *Py_VaBuildValue(const char *format, va_list vargs)
  Valeur de retour : nouvelle référence. Part of the Stable ABI.

  Identical to `Py_BuildValue()`, except that it accepts a va_list rather than a variable number of arguments.