.. highlight:: c
.. _longobjects:
Integer Objects
---------------
.. index:: pair: object; long integer
pair: object; integer
All integers are implemented as "long" integer objects of arbitrary size.
On error, most ``PyLong_As*`` APIs return ``(return type)-1`` which cannot be
distinguished from a number. Use :c:func:`PyErr_Occurred` to disambiguate.
.. c:type:: PyLongObject
This subtype of :c:type:`PyObject` represents a Python integer object.
.. c:var:: PyTypeObject PyLong_Type
This instance of :c:type:`PyTypeObject` represents the Python integer type.
This is the same object as :class:`int` in the Python layer.
.. c:function:: int PyLong_Check(PyObject *p)
Return true if its argument is a :c:type:`PyLongObject` or a subtype of
:c:type:`PyLongObject`. This function always succeeds.
.. c:function:: int PyLong_CheckExact(PyObject *p)
Return true if its argument is a :c:type:`PyLongObject`, but not a subtype of
:c:type:`PyLongObject`. This function always succeeds.
.. c:function:: PyObject* PyLong_FromLong(long v)
Return a new :c:type:`PyLongObject` object from *v*, or ``NULL`` on failure.
The current implementation keeps an array of integer objects for all integers
between ``-5`` and ``256``. When you create an int in that range you actually
just get back a reference to the existing object.
.. c:function:: PyObject* PyLong_FromUnsignedLong(unsigned long v)
Return a new :c:type:`PyLongObject` object from a C :c:expr:`unsigned long`, or
``NULL`` on failure.
.. c:function:: PyObject* PyLong_FromSsize_t(Py_ssize_t v)
Return a new :c:type:`PyLongObject` object from a C :c:type:`Py_ssize_t`, or
``NULL`` on failure.
.. c:function:: PyObject* PyLong_FromSize_t(size_t v)
Return a new :c:type:`PyLongObject` object from a C :c:type:`size_t`, or
``NULL`` on failure.
.. c:function:: PyObject* PyLong_FromLongLong(long long v)
Return a new :c:type:`PyLongObject` object from a C :c:expr:`long long`, or ``NULL``
on failure.
.. c:function:: PyObject* PyLong_FromInt32(int32_t value)
PyObject* PyLong_FromInt64(int64_t value)
Return a new :c:type:`PyLongObject` object from a signed C
:c:expr:`int32_t` or :c:expr:`int64_t`, or ``NULL``
with an exception set on failure.
.. versionadded:: 3.14
.. c:function:: PyObject* PyLong_FromUnsignedLongLong(unsigned long long v)
Return a new :c:type:`PyLongObject` object from a C :c:expr:`unsigned long long`,
or ``NULL`` on failure.
.. c:function:: PyObject* PyLong_FromUInt32(uint32_t value)
PyObject* PyLong_FromUInt64(uint64_t value)
Return a new :c:type:`PyLongObject` object from an unsigned C
:c:expr:`uint32_t` or :c:expr:`uint64_t`, or ``NULL``
with an exception set on failure.
.. versionadded:: 3.14
.. c:function:: PyObject* PyLong_FromDouble(double v)
Return a new :c:type:`PyLongObject` object from the integer part of *v*, or
``NULL`` on failure.
.. c:function:: PyObject* PyLong_FromString(const char *str, char **pend, int base)
Return a new :c:type:`PyLongObject` based on the string value in *str*, which
is interpreted according to the radix in *base*, or ``NULL`` on failure. If
*pend* is non-``NULL``, *\*pend* will point to the end of *str* on success or
to the first character that could not be processed on error. If *base* is ``0``,
*str* is interpreted using the :ref:`integers` definition; in this case, leading
zeros in a non-zero decimal number raises a :exc:`ValueError`. If *base* is not
``0``, it must be between ``2`` and ``36``, inclusive. Leading and trailing
whitespace and single underscores after a base specifier and between digits are
ignored. If there are no digits or *str* is not NULL-terminated following the
digits and trailing whitespace, :exc:`ValueError` will be raised.
.. seealso:: :c:func:`PyLong_AsNativeBytes()` and
:c:func:`PyLong_FromNativeBytes()` functions can be used to convert
a :c:type:`PyLongObject` to/from an array of bytes in base ``256``.
.. c:function:: PyObject* PyLong_FromUnicodeObject(PyObject *u, int base)
Convert a sequence of Unicode digits in the string *u* to a Python integer
value.
.. versionadded:: 3.3
.. c:function:: PyObject* PyLong_FromVoidPtr(void *p)
Create a Python integer from the pointer *p*. The pointer value can be
retrieved from the resulting value using :c:func:`PyLong_AsVoidPtr`.
.. c:function:: PyObject* PyLong_FromNativeBytes(const void* buffer, size_t n_bytes, int flags)
Create a Python integer from the value contained in the first *n_bytes* of
*buffer*, interpreted as a two's-complement signed number.
*flags* are as for :c:func:`PyLong_AsNativeBytes`. Passing ``-1`` will select
the native endian that CPython was compiled with and assume that the
most-significant bit is a sign bit. Passing
``Py_ASNATIVEBYTES_UNSIGNED_BUFFER`` will produce the same result as calling
:c:func:`PyLong_FromUnsignedNativeBytes`. Other flags are ignored.
.. versionadded:: 3.13
.. c:function:: PyObject* PyLong_FromUnsignedNativeBytes(const void* buffer, size_t n_bytes, int flags)
Create a Python integer from the value contained in the first *n_bytes* of
*buffer*, interpreted as an unsigned number.
*flags* are as for :c:func:`PyLong_AsNativeBytes`. Passing ``-1`` will select
the native endian that CPython was compiled with and assume that the
most-significant bit is not a sign bit. Flags other than endian are ignored.
.. versionadded:: 3.13
.. XXX alias PyLong_AS_LONG (for now)
.. c:function:: long PyLong_AsLong(PyObject *obj)
.. index::
single: LONG_MAX (C macro)
single: OverflowError (built-in exception)
Return a C :c:expr:`long` representation of *obj*. If *obj* is not an
instance of :c:type:`PyLongObject`, first call its :meth:`~object.__index__` method
(if present) to convert it to a :c:type:`PyLongObject`.
Raise :exc:`OverflowError` if the value of *obj* is out of range for a
:c:expr:`long`.
Returns ``-1`` on error. Use :c:func:`PyErr_Occurred` to disambiguate.
.. versionchanged:: 3.8
Use :meth:`~object.__index__` if available.
.. versionchanged:: 3.10
This function will no longer use :meth:`~object.__int__`.
.. c:function:: int PyLong_AsInt(PyObject *obj)
Similar to :c:func:`PyLong_AsLong`, but store the result in a C
:c:expr:`int` instead of a C :c:expr:`long`.
.. versionadded:: 3.13
.. c:function:: long PyLong_AsLongAndOverflow(PyObject *obj, int *overflow)
Return a C :c:expr:`long` representation of *obj*. If *obj* is not an
instance of :c:type:`PyLongObject`, first call its :meth:`~object.__index__`
method (if present) to convert it to a :c:type:`PyLongObject`.
If the value of *obj* is greater than :c:macro:`LONG_MAX` or less than
:c:macro:`LONG_MIN`, set *\*overflow* to ``1`` or ``-1``, respectively, and
return ``-1``; otherwise, set *\*overflow* to ``0``. If any other exception
occurs set *\*overflow* to ``0`` and return ``-1`` as usual.
Returns ``-1`` on error. Use :c:func:`PyErr_Occurred` to disambiguate.
.. versionchanged:: 3.8
Use :meth:`~object.__index__` if available.
.. versionchanged:: 3.10
This function will no longer use :meth:`~object.__int__`.
.. c:function:: long long PyLong_AsLongLong(PyObject *obj)
.. index::
single: OverflowError (built-in exception)
Return a C :c:expr:`long long` representation of *obj*. If *obj* is not an
instance of :c:type:`PyLongObject`, first call its :meth:`~object.__index__` method
(if present) to convert it to a :c:type:`PyLongObject`.
Raise :exc:`OverflowError` if the value of *obj* is out of range for a
:c:expr:`long long`.
Returns ``-1`` on error. Use :c:func:`PyErr_Occurred` to disambiguate.
.. versionchanged:: 3.8
Use :meth:`~object.__index__` if available.
.. versionchanged:: 3.10
This function will no longer use :meth:`~object.__int__`.
.. c:function:: long long PyLong_AsLongLongAndOverflow(PyObject *obj, int *overflow)
Return a C :c:expr:`long long` representation of *obj*. If *obj* is not an
instance of :c:type:`PyLongObject`, first call its :meth:`~object.__index__` method
(if present) to convert it to a :c:type:`PyLongObject`.
If the value of *obj* is greater than :c:macro:`LLONG_MAX` or less than
:c:macro:`LLONG_MIN`, set *\*overflow* to ``1`` or ``-1``, respectively,
and return ``-1``; otherwise, set *\*overflow* to ``0``. If any other
exception occurs set *\*overflow* to ``0`` and return ``-1`` as usual.
Returns ``-1`` on error. Use :c:func:`PyErr_Occurred` to disambiguate.
.. versionadded:: 3.2
.. versionchanged:: 3.8
Use :meth:`~object.__index__` if available.
.. versionchanged:: 3.10
This function will no longer use :meth:`~object.__int__`.
.. c:function:: Py_ssize_t PyLong_AsSsize_t(PyObject *pylong)
.. index::
single: PY_SSIZE_T_MAX (C macro)
single: OverflowError (built-in exception)
Return a C :c:type:`Py_ssize_t` representation of *pylong*. *pylong* must
be an instance of :c:type:`PyLongObject`.
Raise :exc:`OverflowError` if the value of *pylong* is out of range for a
:c:type:`Py_ssize_t`.
Returns ``-1`` on error. Use :c:func:`PyErr_Occurred` to disambiguate.
.. c:function:: unsigned long PyLong_AsUnsignedLong(PyObject *pylong)
.. index::
single: ULONG_MAX (C macro)
single: OverflowError (built-in exception)
Return a C :c:expr:`unsigned long` representation of *pylong*. *pylong*
must be an instance of :c:type:`PyLongObject`.
Raise :exc:`OverflowError` if the value of *pylong* is out of range for a
:c:expr:`unsigned long`.
Returns ``(unsigned long)-1`` on error.
Use :c:func:`PyErr_Occurred` to disambiguate.
.. c:function:: size_t PyLong_AsSize_t(PyObject *pylong)
.. index::
single: SIZE_MAX (C macro)
single: OverflowError (built-in exception)
Return a C :c:type:`size_t` representation of *pylong*. *pylong* must be
an instance of :c:type:`PyLongObject`.
Raise :exc:`OverflowError` if the value of *pylong* is out of range for a
:c:type:`size_t`.
Returns ``(size_t)-1`` on error.
Use :c:func:`PyErr_Occurred` to disambiguate.
.. c:function:: unsigned long long PyLong_AsUnsignedLongLong(PyObject *pylong)
.. index::
single: OverflowError (built-in exception)
Return a C :c:expr:`unsigned long long` representation of *pylong*. *pylong*
must be an instance of :c:type:`PyLongObject`.
Raise :exc:`OverflowError` if the value of *pylong* is out of range for an
:c:expr:`unsigned long long`.
Returns ``(unsigned long long)-1`` on error.
Use :c:func:`PyErr_Occurred` to disambiguate.
.. versionchanged:: 3.1
A negative *pylong* now raises :exc:`OverflowError`, not :exc:`TypeError`.
.. c:function:: unsigned long PyLong_AsUnsignedLongMask(PyObject *obj)
Return a C :c:expr:`unsigned long` representation of *obj*. If *obj* is not
an instance of :c:type:`PyLongObject`, first call its :meth:`~object.__index__`
method (if present) to convert it to a :c:type:`PyLongObject`.
If the value of *obj* is out of range for an :c:expr:`unsigned long`,
return the reduction of that value modulo ``ULONG_MAX + 1``.
Returns ``(unsigned long)-1`` on error. Use :c:func:`PyErr_Occurred` to
disambiguate.
.. versionchanged:: 3.8
Use :meth:`~object.__index__` if available.
.. versionchanged:: 3.10
This function will no longer use :meth:`~object.__int__`.
.. c:function:: unsigned long long PyLong_AsUnsignedLongLongMask(PyObject *obj)
Return a C :c:expr:`unsigned long long` representation of *obj*. If *obj*
is not an instance of :c:type:`PyLongObject`, first call its
:meth:`~object.__index__` method (if present) to convert it to a
:c:type:`PyLongObject`.
If the value of *obj* is out of range for an :c:expr:`unsigned long long`,
return the reduction of that value modulo ``ULLONG_MAX + 1``.
Returns ``(unsigned long long)-1`` on error. Use :c:func:`PyErr_Occurred`
to disambiguate.
.. versionchanged:: 3.8
Use :meth:`~object.__index__` if available.
.. versionchanged:: 3.10
This function will no longer use :meth:`~object.__int__`.
.. c:function:: int PyLong_AsInt32(PyObject *obj, int32_t *value)
int PyLong_AsInt64(PyObject *obj, int64_t *value)
Set *\*value* to a signed C :c:expr:`int32_t` or :c:expr:`int64_t`
representation of *obj*.
If the *obj* value is out of range, raise an :exc:`OverflowError`.
Set *\*value* and return ``0`` on success.
Set an exception and return ``-1`` on error.
*value* must not be ``NULL``.
.. versionadded:: 3.14
.. c:function:: int PyLong_AsUInt32(PyObject *obj, uint32_t *value)
int PyLong_AsUInt64(PyObject *obj, uint64_t *value)
Set *\*value* to an unsigned C :c:expr:`uint32_t` or :c:expr:`uint64_t`
representation of *obj*.
If *obj* is not an instance of :c:type:`PyLongObject`, first call its
:meth:`~object.__index__` method (if present) to convert it to a
:c:type:`PyLongObject`.
* If *obj* is negative, raise a :exc:`ValueError`.
* If the *obj* value is out of range, raise an :exc:`OverflowError`.
Set *\*value* and return ``0`` on success.
Set an exception and return ``-1`` on error.
*value* must not be ``NULL``.
.. versionadded:: 3.14
.. c:function:: double PyLong_AsDouble(PyObject *pylong)
Return a C :c:expr:`double` representation of *pylong*. *pylong* must be
an instance of :c:type:`PyLongObject`.
Raise :exc:`OverflowError` if the value of *pylong* is out of range for a
:c:expr:`double`.
Returns ``-1.0`` on error. Use :c:func:`PyErr_Occurred` to disambiguate.
.. c:function:: void* PyLong_AsVoidPtr(PyObject *pylong)
Convert a Python integer *pylong* to a C :c:expr:`void` pointer.
If *pylong* cannot be converted, an :exc:`OverflowError` will be raised. This
is only assured to produce a usable :c:expr:`void` pointer for values created
with :c:func:`PyLong_FromVoidPtr`.
Returns ``NULL`` on error. Use :c:func:`PyErr_Occurred` to disambiguate.
.. c:function:: Py_ssize_t PyLong_AsNativeBytes(PyObject *pylong, void* buffer, Py_ssize_t n_bytes, int flags)
Copy the Python integer value *pylong* to a native *buffer* of size
*n_bytes*. The *flags* can be set to ``-1`` to behave similarly to a C cast,
or to values documented below to control the behavior.
Returns ``-1`` with an exception raised on error. This may happen if
*pylong* cannot be interpreted as an integer, or if *pylong* was negative
and the ``Py_ASNATIVEBYTES_REJECT_NEGATIVE`` flag was set.
Otherwise, returns the number of bytes required to store the value.
If this is equal to or less than *n_bytes*, the entire value was copied.
All *n_bytes* of the buffer are written: large buffers are padded with
zeroes.
If the returned value is greater than than *n_bytes*, the value was
truncated: as many of the lowest bits of the value as could fit are written,
and the higher bits are ignored. This matches the typical behavior
of a C-style downcast.
.. note::
Overflow is not considered an error. If the returned value
is larger than *n_bytes*, most significant bits were discarded.
``0`` will never be returned.
Values are always copied as two's-complement.
Usage example::
int32_t value;
Py_ssize_t bytes = PyLong_AsNativeBytes(pylong, &value, sizeof(value), -1);
if (bytes < 0) {
// Failed. A Python exception was set with the reason.
return NULL;
}
else if (bytes <= (Py_ssize_t)sizeof(value)) {
// Success!
}
else {
// Overflow occurred, but 'value' contains the truncated
// lowest bits of pylong.
}
Passing zero to *n_bytes* will return the size of a buffer that would
be large enough to hold the value. This may be larger than technically
necessary, but not unreasonably so. If *n_bytes=0*, *buffer* may be
``NULL``.
.. note::
Passing *n_bytes=0* to this function is not an accurate way to determine
the bit length of the value.
To get at the entire Python value of an unknown size, the function can be
called twice: first to determine the buffer size, then to fill it::
// Ask how much space we need.
Py_ssize_t expected = PyLong_AsNativeBytes(pylong, NULL, 0, -1);
if (expected < 0) {
// Failed. A Python exception was set with the reason.
return NULL;
}
assert(expected != 0); // Impossible per the API definition.
uint8_t *bignum = malloc(expected);
if (!bignum) {
PyErr_SetString(PyExc_MemoryError, "bignum malloc failed.");
return NULL;
}
// Safely get the entire value.
Py_ssize_t bytes = PyLong_AsNativeBytes(pylong, bignum, expected, -1);
if (bytes < 0) { // Exception has been set.
free(bignum);
return NULL;
}
else if (bytes > expected) { // This should not be possible.
PyErr_SetString(PyExc_RuntimeError,
"Unexpected bignum truncation after a size check.");
free(bignum);
return NULL;
}
// The expected success given the above pre-check.
// ... use bignum ...
free(bignum);
*flags* is either ``-1`` (``Py_ASNATIVEBYTES_DEFAULTS``) to select defaults
that behave most like a C cast, or a combintation of the other flags in
the table below.
Note that ``-1`` cannot be combined with other flags.
Currently, ``-1`` corresponds to
``Py_ASNATIVEBYTES_NATIVE_ENDIAN | Py_ASNATIVEBYTES_UNSIGNED_BUFFER``.
============================================= ======
Flag Value
============================================= ======
.. c:macro:: Py_ASNATIVEBYTES_DEFAULTS ``-1``
.. c:macro:: Py_ASNATIVEBYTES_BIG_ENDIAN ``0``
.. c:macro:: Py_ASNATIVEBYTES_LITTLE_ENDIAN ``1``
.. c:macro:: Py_ASNATIVEBYTES_NATIVE_ENDIAN ``3``
.. c:macro:: Py_ASNATIVEBYTES_UNSIGNED_BUFFER ``4``
.. c:macro:: Py_ASNATIVEBYTES_REJECT_NEGATIVE ``8``
.. c:macro:: Py_ASNATIVEBYTES_ALLOW_INDEX ``16``
============================================= ======
Specifying ``Py_ASNATIVEBYTES_NATIVE_ENDIAN`` will override any other endian
flags. Passing ``2`` is reserved.
By default, sufficient buffer will be requested to include a sign bit.
For example, when converting 128 with *n_bytes=1*, the function will return
2 (or more) in order to store a zero sign bit.
If ``Py_ASNATIVEBYTES_UNSIGNED_BUFFER`` is specified, a zero sign bit
will be omitted from size calculations. This allows, for example, 128 to fit
in a single-byte buffer. If the destination buffer is later treated as
signed, a positive input value may become negative.
Note that the flag does not affect handling of negative values: for those,
space for a sign bit is always requested.
Specifying ``Py_ASNATIVEBYTES_REJECT_NEGATIVE`` causes an exception to be set
if *pylong* is negative. Without this flag, negative values will be copied
provided there is enough space for at least one sign bit, regardless of
whether ``Py_ASNATIVEBYTES_UNSIGNED_BUFFER`` was specified.
If ``Py_ASNATIVEBYTES_ALLOW_INDEX`` is specified and a non-integer value is
passed, its :meth:`~object.__index__` method will be called first. This may
result in Python code executing and other threads being allowed to run, which
could cause changes to other objects or values in use. When *flags* is
``-1``, this option is not set, and non-integer values will raise
:exc:`TypeError`.
.. note::
With the default *flags* (``-1``, or *UNSIGNED_BUFFER* without
*REJECT_NEGATIVE*), multiple Python integers can map to a single value
without overflow. For example, both ``255`` and ``-1`` fit a single-byte
buffer and set all its bits.
This matches typical C cast behavior.
.. versionadded:: 3.13
.. c:function:: int PyLong_GetSign(PyObject *obj, int *sign)
Get the sign of the integer object *obj*.
On success, set *\*sign* to the integer sign (0, -1 or +1 for zero, negative or
positive integer, respectively) and return 0.
On failure, return -1 with an exception set. This function always succeeds
if *obj* is a :c:type:`PyLongObject` or its subtype.
.. versionadded:: 3.14
.. c:function:: PyObject* PyLong_GetInfo(void)
On success, return a read only :term:`named tuple`, that holds
information about Python's internal representation of integers.
See :data:`sys.int_info` for description of individual fields.
On failure, return ``NULL`` with an exception set.
.. versionadded:: 3.1
.. c:function:: int PyUnstable_Long_IsCompact(const PyLongObject* op)
Return 1 if *op* is compact, 0 otherwise.
This function makes it possible for performance-critical code to implement
a “fast path” for small integers. For compact values use
:c:func:`PyUnstable_Long_CompactValue`; for others fall back to a
:c:func:`PyLong_As* <PyLong_AsSize_t>` function or
:c:func:`PyLong_AsNativeBytes`.
The speedup is expected to be negligible for most users.
Exactly what values are considered compact is an implementation detail
and is subject to change.
.. c:function:: Py_ssize_t PyUnstable_Long_CompactValue(const PyLongObject* op)
If *op* is compact, as determined by :c:func:`PyUnstable_Long_IsCompact`,
return its value.
Otherwise, the return value is undefined.
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