.. index:: pair: object; long integer
pair: object; integerAll 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_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_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:: Python methods :meth:`int.to_bytes` and :meth:`int.from_bytes`
to convert a :c:type:`PyLongObject` to/from an array of bytes in base
``256``. You can call those from C using :c:func:`PyObject_CallMethod`.
.. 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
.. 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:: 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_AsNativeBits(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.
.. note::
Passing *n_bytes=0* to this function is not an accurate way to determine
the bit length of a value.
If *n_bytes=0*, *buffer* may be ``NULL``.
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_AsNativeBits(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_AsNativeBits(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``
============================================= ======
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.
.. 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 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.