cpython/Doc/c-api/abstract.rst

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.. highlightlang:: c
.. _abstract:
**********************
Abstract Objects Layer
**********************
The functions in this chapter interact with Python objects regardless of their
type, or with wide classes of object types (e.g. all numerical types, or all
sequence types). When used on object types for which they do not apply, they
will raise a Python exception.
It is not possible to use these functions on objects that are not properly
initialized, such as a list object that has been created by :cfunc:`PyList_New`,
but whose items have not been set to some non-\ ``NULL`` value yet.
.. _object:
Object Protocol
===============
.. cfunction:: int PyObject_Print(PyObject *o, FILE *fp, int flags)
Print an object *o*, on file *fp*. Returns ``-1`` on error. The flags argument
is used to enable certain printing options. The only option currently supported
is :const:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written
instead of the :func:`repr`.
.. cfunction:: int PyObject_HasAttrString(PyObject *o, const char *attr_name)
Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise. This
is equivalent to the Python expression ``hasattr(o, attr_name)``. This function
always succeeds.
.. cfunction:: PyObject* PyObject_GetAttrString(PyObject *o, const char *attr_name)
Retrieve an attribute named *attr_name* from object *o*. Returns the attribute
value on success, or *NULL* on failure. This is the equivalent of the Python
expression ``o.attr_name``.
.. cfunction:: int PyObject_HasAttr(PyObject *o, PyObject *attr_name)
Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise. This
is equivalent to the Python expression ``hasattr(o, attr_name)``. This function
always succeeds.
.. cfunction:: PyObject* PyObject_GetAttr(PyObject *o, PyObject *attr_name)
Retrieve an attribute named *attr_name* from object *o*. Returns the attribute
value on success, or *NULL* on failure. This is the equivalent of the Python
expression ``o.attr_name``.
.. cfunction:: int PyObject_SetAttrString(PyObject *o, const char *attr_name, PyObject *v)
Set the value of the attribute named *attr_name*, for object *o*, to the value
*v*. Returns ``-1`` on failure. This is the equivalent of the Python statement
``o.attr_name = v``.
.. cfunction:: int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v)
Set the value of the attribute named *attr_name*, for object *o*, to the value
*v*. Returns ``-1`` on failure. This is the equivalent of the Python statement
``o.attr_name = v``.
.. cfunction:: int PyObject_DelAttrString(PyObject *o, const char *attr_name)
Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.
This is the equivalent of the Python statement: ``del o.attr_name``.
.. cfunction:: int PyObject_DelAttr(PyObject *o, PyObject *attr_name)
Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.
This is the equivalent of the Python statement ``del o.attr_name``.
.. cfunction:: PyObject* PyObject_RichCompare(PyObject *o1, PyObject *o2, int opid)
Compare the values of *o1* and *o2* using the operation specified by *opid*,
which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,
:const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ``<``,
``<=``, ``==``, ``!=``, ``>``, or ``>=`` respectively. This is the equivalent of
the Python expression ``o1 op o2``, where ``op`` is the operator corresponding
to *opid*. Returns the value of the comparison on success, or *NULL* on failure.
.. cfunction:: int PyObject_RichCompareBool(PyObject *o1, PyObject *o2, int opid)
Compare the values of *o1* and *o2* using the operation specified by *opid*,
which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,
:const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ``<``,
``<=``, ``==``, ``!=``, ``>``, or ``>=`` respectively. Returns ``-1`` on error,
``0`` if the result is false, ``1`` otherwise. This is the equivalent of the
Python expression ``o1 op o2``, where ``op`` is the operator corresponding to
*opid*.
.. cfunction:: int PyObject_Cmp(PyObject *o1, PyObject *o2, int *result)
.. index:: builtin: cmp
Compare the values of *o1* and *o2* using a routine provided by *o1*, if one
exists, otherwise with a routine provided by *o2*. The result of the comparison
is returned in *result*. Returns ``-1`` on failure. This is the equivalent of
the Python statement ``result = cmp(o1, o2)``.
.. cfunction:: int PyObject_Compare(PyObject *o1, PyObject *o2)
.. index:: builtin: cmp
Compare the values of *o1* and *o2* using a routine provided by *o1*, if one
exists, otherwise with a routine provided by *o2*. Returns the result of the
comparison on success. On error, the value returned is undefined; use
:cfunc:`PyErr_Occurred` to detect an error. This is equivalent to the Python
expression ``cmp(o1, o2)``.
.. cfunction:: PyObject* PyObject_Repr(PyObject *o)
.. index:: builtin: repr
Compute a string representation of object *o*. Returns the string
representation on success, *NULL* on failure. This is the equivalent of the
Python expression ``repr(o)``. Called by the :func:`repr` built-in function and
by reverse quotes.
.. cfunction:: PyObject* PyObject_Str(PyObject *o)
.. index:: builtin: str
Compute a string representation of object *o*. Returns the string
representation on success, *NULL* on failure. This is the equivalent of the
Python expression ``str(o)``. Called by the :func:`str` built-in function and
by the :keyword:`print` statement.
.. cfunction:: PyObject* PyObject_Unicode(PyObject *o)
.. index:: builtin: unicode
Compute a Unicode string representation of object *o*. Returns the Unicode
string representation on success, *NULL* on failure. This is the equivalent of
the Python expression ``unicode(o)``. Called by the :func:`unicode` built-in
function.
.. cfunction:: int PyObject_IsInstance(PyObject *inst, PyObject *cls)
Returns ``1`` if *inst* is an instance of the class *cls* or a subclass of
*cls*, or ``0`` if not. On error, returns ``-1`` and sets an exception. If
*cls* is a type object rather than a class object, :cfunc:`PyObject_IsInstance`
returns ``1`` if *inst* is of type *cls*. If *cls* is a tuple, the check will
be done against every entry in *cls*. The result will be ``1`` when at least one
of the checks returns ``1``, otherwise it will be ``0``. If *inst* is not a
class instance and *cls* is neither a type object, nor a class object, nor a
tuple, *inst* must have a :attr:`__class__` attribute --- the class relationship
of the value of that attribute with *cls* will be used to determine the result
of this function.
.. versionadded:: 2.1
.. versionchanged:: 2.2
Support for a tuple as the second argument added.
Subclass determination is done in a fairly straightforward way, but includes a
wrinkle that implementors of extensions to the class system may want to be aware
of. If :class:`A` and :class:`B` are class objects, :class:`B` is a subclass of
:class:`A` if it inherits from :class:`A` either directly or indirectly. If
either is not a class object, a more general mechanism is used to determine the
class relationship of the two objects. When testing if *B* is a subclass of
*A*, if *A* is *B*, :cfunc:`PyObject_IsSubclass` returns true. If *A* and *B*
are different objects, *B*'s :attr:`__bases__` attribute is searched in a
depth-first fashion for *A* --- the presence of the :attr:`__bases__` attribute
is considered sufficient for this determination.
.. cfunction:: int PyObject_IsSubclass(PyObject *derived, PyObject *cls)
Returns ``1`` if the class *derived* is identical to or derived from the class
*cls*, otherwise returns ``0``. In case of an error, returns ``-1``. If *cls*
is a tuple, the check will be done against every entry in *cls*. The result will
be ``1`` when at least one of the checks returns ``1``, otherwise it will be
``0``. If either *derived* or *cls* is not an actual class object (or tuple),
this function uses the generic algorithm described above.
.. versionadded:: 2.1
.. versionchanged:: 2.3
Older versions of Python did not support a tuple as the second argument.
.. cfunction:: int PyCallable_Check(PyObject *o)
Determine if the object *o* is callable. Return ``1`` if the object is callable
and ``0`` otherwise. This function always succeeds.
.. cfunction:: PyObject* PyObject_Call(PyObject *callable_object, PyObject *args, PyObject *kw)
.. index:: builtin: apply
Call a callable Python object *callable_object*, with arguments given by the
tuple *args*, and named arguments given by the dictionary *kw*. If no named
arguments are needed, *kw* may be *NULL*. *args* must not be *NULL*, use an
empty tuple if no arguments are needed. Returns the result of the call on
success, or *NULL* on failure. This is the equivalent of the Python expression
``apply(callable_object, args, kw)`` or ``callable_object(*args, **kw)``.
.. versionadded:: 2.2
.. cfunction:: PyObject* PyObject_CallObject(PyObject *callable_object, PyObject *args)
.. index:: builtin: apply
Call a callable Python object *callable_object*, with arguments given by the
tuple *args*. If no arguments are needed, then *args* may be *NULL*. Returns
the result of the call on success, or *NULL* on failure. This is the equivalent
of the Python expression ``apply(callable_object, args)`` or
``callable_object(*args)``.
.. cfunction:: PyObject* PyObject_CallFunction(PyObject *callable, char *format, ...)
.. index:: builtin: apply
Call a callable Python object *callable*, with a variable number of C arguments.
The C arguments are described using a :cfunc:`Py_BuildValue` style format
string. The format may be *NULL*, indicating that no arguments are provided.
Returns the result of the call on success, or *NULL* on failure. This is the
equivalent of the Python expression ``apply(callable, args)`` or
``callable(*args)``. Note that if you only pass :ctype:`PyObject \*` args,
:cfunc:`PyObject_CallFunctionObjArgs` is a faster alternative.
.. cfunction:: PyObject* PyObject_CallMethod(PyObject *o, char *method, char *format, ...)
Call the method named *method* of object *o* with a variable number of C
arguments. The C arguments are described by a :cfunc:`Py_BuildValue` format
string that should produce a tuple. The format may be *NULL*, indicating that
no arguments are provided. Returns the result of the call on success, or *NULL*
on failure. This is the equivalent of the Python expression ``o.method(args)``.
Note that if you only pass :ctype:`PyObject \*` args,
:cfunc:`PyObject_CallMethodObjArgs` is a faster alternative.
.. cfunction:: PyObject* PyObject_CallFunctionObjArgs(PyObject *callable, ..., NULL)
Call a callable Python object *callable*, with a variable number of
:ctype:`PyObject\*` arguments. The arguments are provided as a variable number
of parameters followed by *NULL*. Returns the result of the call on success, or
*NULL* on failure.
.. versionadded:: 2.2
.. cfunction:: PyObject* PyObject_CallMethodObjArgs(PyObject *o, PyObject *name, ..., NULL)
Calls a method of the object *o*, where the name of the method is given as a
Python string object in *name*. It is called with a variable number of
:ctype:`PyObject\*` arguments. The arguments are provided as a variable number
of parameters followed by *NULL*. Returns the result of the call on success, or
*NULL* on failure.
.. versionadded:: 2.2
.. cfunction:: long PyObject_Hash(PyObject *o)
.. index:: builtin: hash
Compute and return the hash value of an object *o*. On failure, return ``-1``.
This is the equivalent of the Python expression ``hash(o)``.
.. cfunction:: int PyObject_IsTrue(PyObject *o)
Returns ``1`` if the object *o* is considered to be true, and ``0`` otherwise.
This is equivalent to the Python expression ``not not o``. On failure, return
``-1``.
.. cfunction:: int PyObject_Not(PyObject *o)
Returns ``0`` if the object *o* is considered to be true, and ``1`` otherwise.
This is equivalent to the Python expression ``not o``. On failure, return
``-1``.
.. cfunction:: PyObject* PyObject_Type(PyObject *o)
.. index:: builtin: type
When *o* is non-*NULL*, returns a type object corresponding to the object type
of object *o*. On failure, raises :exc:`SystemError` and returns *NULL*. This
is equivalent to the Python expression ``type(o)``. This function increments the
reference count of the return value. There's really no reason to use this
function instead of the common expression ``o->ob_type``, which returns a
pointer of type :ctype:`PyTypeObject\*`, except when the incremented reference
count is needed.
.. cfunction:: int PyObject_TypeCheck(PyObject *o, PyTypeObject *type)
Return true if the object *o* is of type *type* or a subtype of *type*. Both
parameters must be non-*NULL*.
.. versionadded:: 2.2
.. cfunction:: Py_ssize_t PyObject_Length(PyObject *o)
Py_ssize_t PyObject_Size(PyObject *o)
.. index:: builtin: len
Return the length of object *o*. If the object *o* provides either the sequence
and mapping protocols, the sequence length is returned. On error, ``-1`` is
returned. This is the equivalent to the Python expression ``len(o)``.
.. cfunction:: PyObject* PyObject_GetItem(PyObject *o, PyObject *key)
Return element of *o* corresponding to the object *key* or *NULL* on failure.
This is the equivalent of the Python expression ``o[key]``.
.. cfunction:: int PyObject_SetItem(PyObject *o, PyObject *key, PyObject *v)
Map the object *key* to the value *v*. Returns ``-1`` on failure. This is the
equivalent of the Python statement ``o[key] = v``.
.. cfunction:: int PyObject_DelItem(PyObject *o, PyObject *key)
Delete the mapping for *key* from *o*. Returns ``-1`` on failure. This is the
equivalent of the Python statement ``del o[key]``.
.. cfunction:: int PyObject_AsFileDescriptor(PyObject *o)
Derives a file-descriptor from a Python object. If the object is an integer or
long integer, its value is returned. If not, the object's :meth:`fileno` method
is called if it exists; the method must return an integer or long integer, which
is returned as the file descriptor value. Returns ``-1`` on failure.
.. cfunction:: PyObject* PyObject_Dir(PyObject *o)
This is equivalent to the Python expression ``dir(o)``, returning a (possibly
empty) list of strings appropriate for the object argument, or *NULL* if there
was an error. If the argument is *NULL*, this is like the Python ``dir()``,
returning the names of the current locals; in this case, if no execution frame
is active then *NULL* is returned but :cfunc:`PyErr_Occurred` will return false.
.. cfunction:: PyObject* PyObject_GetIter(PyObject *o)
This is equivalent to the Python expression ``iter(o)``. It returns a new
iterator for the object argument, or the object itself if the object is already
an iterator. Raises :exc:`TypeError` and returns *NULL* if the object cannot be
iterated.
.. _number:
Number Protocol
===============
.. cfunction:: int PyNumber_Check(PyObject *o)
Returns ``1`` if the object *o* provides numeric protocols, and false otherwise.
This function always succeeds.
.. cfunction:: PyObject* PyNumber_Add(PyObject *o1, PyObject *o2)
Returns the result of adding *o1* and *o2*, or *NULL* on failure. This is the
equivalent of the Python expression ``o1 + o2``.
.. cfunction:: PyObject* PyNumber_Subtract(PyObject *o1, PyObject *o2)
Returns the result of subtracting *o2* from *o1*, or *NULL* on failure. This is
the equivalent of the Python expression ``o1 - o2``.
.. cfunction:: PyObject* PyNumber_Multiply(PyObject *o1, PyObject *o2)
Returns the result of multiplying *o1* and *o2*, or *NULL* on failure. This is
the equivalent of the Python expression ``o1 * o2``.
.. cfunction:: PyObject* PyNumber_Divide(PyObject *o1, PyObject *o2)
Returns the result of dividing *o1* by *o2*, or *NULL* on failure. This is the
equivalent of the Python expression ``o1 / o2``.
.. cfunction:: PyObject* PyNumber_FloorDivide(PyObject *o1, PyObject *o2)
Return the floor of *o1* divided by *o2*, or *NULL* on failure. This is
equivalent to the "classic" division of integers.
.. versionadded:: 2.2
.. cfunction:: PyObject* PyNumber_TrueDivide(PyObject *o1, PyObject *o2)
Return a reasonable approximation for the mathematical value of *o1* divided by
*o2*, or *NULL* on failure. The return value is "approximate" because binary
floating point numbers are approximate; it is not possible to represent all real
numbers in base two. This function can return a floating point value when
passed two integers.
.. versionadded:: 2.2
.. cfunction:: PyObject* PyNumber_Remainder(PyObject *o1, PyObject *o2)
Returns the remainder of dividing *o1* by *o2*, or *NULL* on failure. This is
the equivalent of the Python expression ``o1 % o2``.
.. cfunction:: PyObject* PyNumber_Divmod(PyObject *o1, PyObject *o2)
.. index:: builtin: divmod
See the built-in function :func:`divmod`. Returns *NULL* on failure. This is
the equivalent of the Python expression ``divmod(o1, o2)``.
.. cfunction:: PyObject* PyNumber_Power(PyObject *o1, PyObject *o2, PyObject *o3)
.. index:: builtin: pow
See the built-in function :func:`pow`. Returns *NULL* on failure. This is the
equivalent of the Python expression ``pow(o1, o2, o3)``, where *o3* is optional.
If *o3* is to be ignored, pass :cdata:`Py_None` in its place (passing *NULL* for
*o3* would cause an illegal memory access).
.. cfunction:: PyObject* PyNumber_Negative(PyObject *o)
Returns the negation of *o* on success, or *NULL* on failure. This is the
equivalent of the Python expression ``-o``.
.. cfunction:: PyObject* PyNumber_Positive(PyObject *o)
Returns *o* on success, or *NULL* on failure. This is the equivalent of the
Python expression ``+o``.
.. cfunction:: PyObject* PyNumber_Absolute(PyObject *o)
.. index:: builtin: abs
Returns the absolute value of *o*, or *NULL* on failure. This is the equivalent
of the Python expression ``abs(o)``.
.. cfunction:: PyObject* PyNumber_Invert(PyObject *o)
Returns the bitwise negation of *o* on success, or *NULL* on failure. This is
the equivalent of the Python expression ``~o``.
.. cfunction:: PyObject* PyNumber_Lshift(PyObject *o1, PyObject *o2)
Returns the result of left shifting *o1* by *o2* on success, or *NULL* on
failure. This is the equivalent of the Python expression ``o1 << o2``.
.. cfunction:: PyObject* PyNumber_Rshift(PyObject *o1, PyObject *o2)
Returns the result of right shifting *o1* by *o2* on success, or *NULL* on
failure. This is the equivalent of the Python expression ``o1 >> o2``.
.. cfunction:: PyObject* PyNumber_And(PyObject *o1, PyObject *o2)
Returns the "bitwise and" of *o1* and *o2* on success and *NULL* on failure.
This is the equivalent of the Python expression ``o1 & o2``.
.. cfunction:: PyObject* PyNumber_Xor(PyObject *o1, PyObject *o2)
Returns the "bitwise exclusive or" of *o1* by *o2* on success, or *NULL* on
failure. This is the equivalent of the Python expression ``o1 ^ o2``.
.. cfunction:: PyObject* PyNumber_Or(PyObject *o1, PyObject *o2)
Returns the "bitwise or" of *o1* and *o2* on success, or *NULL* on failure.
This is the equivalent of the Python expression ``o1 | o2``.
.. cfunction:: PyObject* PyNumber_InPlaceAdd(PyObject *o1, PyObject *o2)
Returns the result of adding *o1* and *o2*, or *NULL* on failure. The operation
is done *in-place* when *o1* supports it. This is the equivalent of the Python
statement ``o1 += o2``.
.. cfunction:: PyObject* PyNumber_InPlaceSubtract(PyObject *o1, PyObject *o2)
Returns the result of subtracting *o2* from *o1*, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 -= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceMultiply(PyObject *o1, PyObject *o2)
Returns the result of multiplying *o1* and *o2*, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 *= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceDivide(PyObject *o1, PyObject *o2)
Returns the result of dividing *o1* by *o2*, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 /= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceFloorDivide(PyObject *o1, PyObject *o2)
Returns the mathematical floor of dividing *o1* by *o2*, or *NULL* on failure.
The operation is done *in-place* when *o1* supports it. This is the equivalent
of the Python statement ``o1 //= o2``.
.. versionadded:: 2.2
.. cfunction:: PyObject* PyNumber_InPlaceTrueDivide(PyObject *o1, PyObject *o2)
Return a reasonable approximation for the mathematical value of *o1* divided by
*o2*, or *NULL* on failure. The return value is "approximate" because binary
floating point numbers are approximate; it is not possible to represent all real
numbers in base two. This function can return a floating point value when
passed two integers. The operation is done *in-place* when *o1* supports it.
.. versionadded:: 2.2
.. cfunction:: PyObject* PyNumber_InPlaceRemainder(PyObject *o1, PyObject *o2)
Returns the remainder of dividing *o1* by *o2*, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 %= o2``.
.. cfunction:: PyObject* PyNumber_InPlacePower(PyObject *o1, PyObject *o2, PyObject *o3)
.. index:: builtin: pow
See the built-in function :func:`pow`. Returns *NULL* on failure. The operation
is done *in-place* when *o1* supports it. This is the equivalent of the Python
statement ``o1 **= o2`` when o3 is :cdata:`Py_None`, or an in-place variant of
``pow(o1, o2, o3)`` otherwise. If *o3* is to be ignored, pass :cdata:`Py_None`
in its place (passing *NULL* for *o3* would cause an illegal memory access).
.. cfunction:: PyObject* PyNumber_InPlaceLshift(PyObject *o1, PyObject *o2)
Returns the result of left shifting *o1* by *o2* on success, or *NULL* on
failure. The operation is done *in-place* when *o1* supports it. This is the
equivalent of the Python statement ``o1 <<= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceRshift(PyObject *o1, PyObject *o2)
Returns the result of right shifting *o1* by *o2* on success, or *NULL* on
failure. The operation is done *in-place* when *o1* supports it. This is the
equivalent of the Python statement ``o1 >>= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceAnd(PyObject *o1, PyObject *o2)
Returns the "bitwise and" of *o1* and *o2* on success and *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 &= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceXor(PyObject *o1, PyObject *o2)
Returns the "bitwise exclusive or" of *o1* by *o2* on success, or *NULL* on
failure. The operation is done *in-place* when *o1* supports it. This is the
equivalent of the Python statement ``o1 ^= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceOr(PyObject *o1, PyObject *o2)
Returns the "bitwise or" of *o1* and *o2* on success, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 |= o2``.
.. cfunction:: int PyNumber_Coerce(PyObject **p1, PyObject **p2)
.. index:: builtin: coerce
This function takes the addresses of two variables of type :ctype:`PyObject\*`.
If the objects pointed to by ``*p1`` and ``*p2`` have the same type, increment
their reference count and return ``0`` (success). If the objects can be
converted to a common numeric type, replace ``*p1`` and ``*p2`` by their
converted value (with 'new' reference counts), and return ``0``. If no
conversion is possible, or if some other error occurs, return ``-1`` (failure)
and don't increment the reference counts. The call ``PyNumber_Coerce(&o1,
&o2)`` is equivalent to the Python statement ``o1, o2 = coerce(o1, o2)``.
.. cfunction:: PyObject* PyNumber_Int(PyObject *o)
.. index:: builtin: int
Returns the *o* converted to an integer object on success, or *NULL* on failure.
If the argument is outside the integer range a long object will be returned
instead. This is the equivalent of the Python expression ``int(o)``.
.. cfunction:: PyObject* PyNumber_Long(PyObject *o)
.. index:: builtin: long
Returns the *o* converted to a long integer object on success, or *NULL* on
failure. This is the equivalent of the Python expression ``long(o)``.
.. cfunction:: PyObject* PyNumber_Float(PyObject *o)
.. index:: builtin: float
Returns the *o* converted to a float object on success, or *NULL* on failure.
This is the equivalent of the Python expression ``float(o)``.
.. cfunction:: PyObject* PyNumber_Index(PyObject *o)
Returns the *o* converted to a Python int or long on success or *NULL* with a
TypeError exception raised on failure.
.. versionadded:: 2.5
.. cfunction:: Py_ssize_t PyNumber_AsSsize_t(PyObject *o, PyObject *exc)
Returns *o* converted to a Py_ssize_t value if *o* can be interpreted as an
integer. If *o* can be converted to a Python int or long but the attempt to
convert to a Py_ssize_t value would raise an :exc:`OverflowError`, then the
*exc* argument is the type of exception that will be raised (usually
:exc:`IndexError` or :exc:`OverflowError`). If *exc* is *NULL*, then the
exception is cleared and the value is clipped to *PY_SSIZE_T_MIN* for a negative
integer or *PY_SSIZE_T_MAX* for a positive integer.
.. versionadded:: 2.5
.. cfunction:: int PyIndex_Check(PyObject *o)
Returns True if *o* is an index integer (has the nb_index slot of the
tp_as_number structure filled in).
.. versionadded:: 2.5
.. _sequence:
Sequence Protocol
=================
.. cfunction:: int PySequence_Check(PyObject *o)
Return ``1`` if the object provides sequence protocol, and ``0`` otherwise.
This function always succeeds.
.. cfunction:: Py_ssize_t PySequence_Size(PyObject *o)
.. index:: builtin: len
Returns the number of objects in sequence *o* on success, and ``-1`` on failure.
For objects that do not provide sequence protocol, this is equivalent to the
Python expression ``len(o)``.
.. cfunction:: Py_ssize_t PySequence_Length(PyObject *o)
Alternate name for :cfunc:`PySequence_Size`.
.. cfunction:: PyObject* PySequence_Concat(PyObject *o1, PyObject *o2)
Return the concatenation of *o1* and *o2* on success, and *NULL* on failure.
This is the equivalent of the Python expression ``o1 + o2``.
.. cfunction:: PyObject* PySequence_Repeat(PyObject *o, Py_ssize_t count)
Return the result of repeating sequence object *o* *count* times, or *NULL* on
failure. This is the equivalent of the Python expression ``o * count``.
.. cfunction:: PyObject* PySequence_InPlaceConcat(PyObject *o1, PyObject *o2)
Return the concatenation of *o1* and *o2* on success, and *NULL* on failure.
The operation is done *in-place* when *o1* supports it. This is the equivalent
of the Python expression ``o1 += o2``.
.. cfunction:: PyObject* PySequence_InPlaceRepeat(PyObject *o, Py_ssize_t count)
Return the result of repeating sequence object *o* *count* times, or *NULL* on
failure. The operation is done *in-place* when *o* supports it. This is the
equivalent of the Python expression ``o *= count``.
.. cfunction:: PyObject* PySequence_GetItem(PyObject *o, Py_ssize_t i)
Return the *i*th element of *o*, or *NULL* on failure. This is the equivalent of
the Python expression ``o[i]``.
.. cfunction:: PyObject* PySequence_GetSlice(PyObject *o, Py_ssize_t i1, Py_ssize_t i2)
Return the slice of sequence object *o* between *i1* and *i2*, or *NULL* on
failure. This is the equivalent of the Python expression ``o[i1:i2]``.
.. cfunction:: int PySequence_SetItem(PyObject *o, Py_ssize_t i, PyObject *v)
Assign object *v* to the *i*th element of *o*. Returns ``-1`` on failure. This
is the equivalent of the Python statement ``o[i] = v``. This function *does
not* steal a reference to *v*.
.. cfunction:: int PySequence_DelItem(PyObject *o, Py_ssize_t i)
Delete the *i*th element of object *o*. Returns ``-1`` on failure. This is the
equivalent of the Python statement ``del o[i]``.
.. cfunction:: int PySequence_SetSlice(PyObject *o, Py_ssize_t i1, Py_ssize_t i2, PyObject *v)
Assign the sequence object *v* to the slice in sequence object *o* from *i1* to
*i2*. This is the equivalent of the Python statement ``o[i1:i2] = v``.
.. cfunction:: int PySequence_DelSlice(PyObject *o, Py_ssize_t i1, Py_ssize_t i2)
Delete the slice in sequence object *o* from *i1* to *i2*. Returns ``-1`` on
failure. This is the equivalent of the Python statement ``del o[i1:i2]``.
.. cfunction:: Py_ssize_t PySequence_Count(PyObject *o, PyObject *value)
Return the number of occurrences of *value* in *o*, that is, return the number
of keys for which ``o[key] == value``. On failure, return ``-1``. This is
equivalent to the Python expression ``o.count(value)``.
.. cfunction:: int PySequence_Contains(PyObject *o, PyObject *value)
Determine if *o* contains *value*. If an item in *o* is equal to *value*,
return ``1``, otherwise return ``0``. On error, return ``-1``. This is
equivalent to the Python expression ``value in o``.
.. cfunction:: Py_ssize_t PySequence_Index(PyObject *o, PyObject *value)
Return the first index *i* for which ``o[i] == value``. On error, return
``-1``. This is equivalent to the Python expression ``o.index(value)``.
.. cfunction:: PyObject* PySequence_List(PyObject *o)
Return a list object with the same contents as the arbitrary sequence *o*. The
returned list is guaranteed to be new.
.. cfunction:: PyObject* PySequence_Tuple(PyObject *o)
.. index:: builtin: tuple
Return a tuple object with the same contents as the arbitrary sequence *o* or
*NULL* on failure. If *o* is a tuple, a new reference will be returned,
otherwise a tuple will be constructed with the appropriate contents. This is
equivalent to the Python expression ``tuple(o)``.
.. cfunction:: PyObject* PySequence_Fast(PyObject *o, const char *m)
Returns the sequence *o* as a tuple, unless it is already a tuple or list, in
which case *o* is returned. Use :cfunc:`PySequence_Fast_GET_ITEM` to access the
members of the result. Returns *NULL* on failure. If the object is not a
sequence, raises :exc:`TypeError` with *m* as the message text.
.. cfunction:: PyObject* PySequence_Fast_GET_ITEM(PyObject *o, Py_ssize_t i)
Return the *i*th element of *o*, assuming that *o* was returned by
:cfunc:`PySequence_Fast`, *o* is not *NULL*, and that *i* is within bounds.
.. cfunction:: PyObject** PySequence_Fast_ITEMS(PyObject *o)
Return the underlying array of PyObject pointers. Assumes that *o* was returned
by :cfunc:`PySequence_Fast` and *o* is not *NULL*.
.. versionadded:: 2.4
.. cfunction:: PyObject* PySequence_ITEM(PyObject *o, Py_ssize_t i)
Return the *i*th element of *o* or *NULL* on failure. Macro form of
:cfunc:`PySequence_GetItem` but without checking that
:cfunc:`PySequence_Check(o)` is true and without adjustment for negative
indices.
.. versionadded:: 2.3
.. cfunction:: Py_ssize_t PySequence_Fast_GET_SIZE(PyObject *o)
Returns the length of *o*, assuming that *o* was returned by
:cfunc:`PySequence_Fast` and that *o* is not *NULL*. The size can also be
gotten by calling :cfunc:`PySequence_Size` on *o*, but
:cfunc:`PySequence_Fast_GET_SIZE` is faster because it can assume *o* is a list
or tuple.
.. _mapping:
Mapping Protocol
================
.. cfunction:: int PyMapping_Check(PyObject *o)
Return ``1`` if the object provides mapping protocol, and ``0`` otherwise. This
function always succeeds.
.. cfunction:: Py_ssize_t PyMapping_Length(PyObject *o)
.. index:: builtin: len
Returns the number of keys in object *o* on success, and ``-1`` on failure. For
objects that do not provide mapping protocol, this is equivalent to the Python
expression ``len(o)``.
.. cfunction:: int PyMapping_DelItemString(PyObject *o, char *key)
Remove the mapping for object *key* from the object *o*. Return ``-1`` on
failure. This is equivalent to the Python statement ``del o[key]``.
.. cfunction:: int PyMapping_DelItem(PyObject *o, PyObject *key)
Remove the mapping for object *key* from the object *o*. Return ``-1`` on
failure. This is equivalent to the Python statement ``del o[key]``.
.. cfunction:: int PyMapping_HasKeyString(PyObject *o, char *key)
On success, return ``1`` if the mapping object has the key *key* and ``0``
otherwise. This is equivalent to the Python expression ``o.has_key(key)``.
This function always succeeds.
.. cfunction:: int PyMapping_HasKey(PyObject *o, PyObject *key)
Return ``1`` if the mapping object has the key *key* and ``0`` otherwise. This
is equivalent to the Python expression ``o.has_key(key)``. This function always
succeeds.
.. cfunction:: PyObject* PyMapping_Keys(PyObject *o)
On success, return a list of the keys in object *o*. On failure, return *NULL*.
This is equivalent to the Python expression ``o.keys()``.
.. cfunction:: PyObject* PyMapping_Values(PyObject *o)
On success, return a list of the values in object *o*. On failure, return
*NULL*. This is equivalent to the Python expression ``o.values()``.
.. cfunction:: PyObject* PyMapping_Items(PyObject *o)
On success, return a list of the items in object *o*, where each item is a tuple
containing a key-value pair. On failure, return *NULL*. This is equivalent to
the Python expression ``o.items()``.
.. cfunction:: PyObject* PyMapping_GetItemString(PyObject *o, char *key)
Return element of *o* corresponding to the object *key* or *NULL* on failure.
This is the equivalent of the Python expression ``o[key]``.
.. cfunction:: int PyMapping_SetItemString(PyObject *o, char *key, PyObject *v)
Map the object *key* to the value *v* in object *o*. Returns ``-1`` on failure.
This is the equivalent of the Python statement ``o[key] = v``.
.. _iterator:
Iterator Protocol
=================
.. versionadded:: 2.2
There are only a couple of functions specifically for working with iterators.
.. cfunction:: int PyIter_Check(PyObject *o)
Return true if the object *o* supports the iterator protocol.
.. cfunction:: PyObject* PyIter_Next(PyObject *o)
Return the next value from the iteration *o*. If the object is an iterator,
this retrieves the next value from the iteration, and returns *NULL* with no
exception set if there are no remaining items. If the object is not an
iterator, :exc:`TypeError` is raised, or if there is an error in retrieving the
item, returns *NULL* and passes along the exception.
To write a loop which iterates over an iterator, the C code should look
something like this::
PyObject *iterator = PyObject_GetIter(obj);
PyObject *item;
if (iterator == NULL) {
/* propagate error */
}
while (item = PyIter_Next(iterator)) {
/* do something with item */
...
/* release reference when done */
Py_DECREF(item);
}
Py_DECREF(iterator);
if (PyErr_Occurred()) {
/* propagate error */
}
else {
/* continue doing useful work */
}
.. _abstract-buffer:
Buffer Protocol
===============
.. cfunction:: int PyObject_AsCharBuffer(PyObject *obj, const char **buffer, Py_ssize_t *buffer_len)
Returns a pointer to a read-only memory location useable as character- based
input. The *obj* argument must support the single-segment character buffer
interface. On success, returns ``0``, sets *buffer* to the memory location and
*buffer_len* to the buffer length. Returns ``-1`` and sets a :exc:`TypeError`
on error.
.. versionadded:: 1.6
.. cfunction:: int PyObject_AsReadBuffer(PyObject *obj, const void **buffer, Py_ssize_t *buffer_len)
Returns a pointer to a read-only memory location containing arbitrary data. The
*obj* argument must support the single-segment readable buffer interface. On
success, returns ``0``, sets *buffer* to the memory location and *buffer_len* to
the buffer length. Returns ``-1`` and sets a :exc:`TypeError` on error.
.. versionadded:: 1.6
.. cfunction:: int PyObject_CheckReadBuffer(PyObject *o)
Returns ``1`` if *o* supports the single-segment readable buffer interface.
Otherwise returns ``0``.
.. versionadded:: 2.2
.. cfunction:: int PyObject_AsWriteBuffer(PyObject *obj, void **buffer, Py_ssize_t *buffer_len)
Returns a pointer to a writeable memory location. The *obj* argument must
support the single-segment, character buffer interface. On success, returns
``0``, sets *buffer* to the memory location and *buffer_len* to the buffer
length. Returns ``-1`` and sets a :exc:`TypeError` on error.
.. versionadded:: 1.6