晋太元中,武陵人捕鱼为业。缘溪行,忘路之远近。忽逢桃花林,夹岸数百步,中无杂树,芳草鲜美,落英缤纷。渔人甚异之,复前行,欲穷其林。 林尽水源,便得一山,山有小口,仿佛若有光。便舍船,从口入。初极狭,才通人。复行数十步,豁然开朗。土地平旷,屋舍俨然,有良田、美池、桑竹之属。阡陌交通,鸡犬相闻。其中往来种作,男女衣着,悉如外人。黄发垂髫,并怡然自乐。 见渔人,乃大惊,问所从来。具答之。便要还家,设酒杀鸡作食。村中闻有此人,咸来问讯。自云先世避秦时乱,率妻子邑人来此绝境,不复出焉,遂与外人间隔。问今是何世,乃不知有汉,无论魏晋。此人一一为具言所闻,皆叹惋。余人各复延至其家,皆出酒食。停数日,辞去。此中人语云:“不足为外人道也。”(间隔 一作:隔绝) 既出,得其船,便扶向路,处处志之。及郡下,诣太守,说如此。太守即遣人随其往,寻向所志,遂迷,不复得路。 南阳刘子骥,高尚士也,闻之,欣然规往。未果,寻病终。后遂无问津者。
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.. highlightlang:: c
.. _longobjects:
Integer Objects
---------------
.. index:: object: long integer
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`.
.. 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`.
.. 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. So it should be possible to
change the value of ``1``. I suspect the behaviour of Python in this case is
undefined. :-)
.. c:function:: PyObject* PyLong_FromUnsignedLong(unsigned long v)
Return a new :c:type:`PyLongObject` object from a C :c:type:`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:type:`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:type:`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*. If *pend* is non-*NULL*,
*\*pend* will point to the first character in *str* which follows the
representation of the number. 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 spaces and single
underscores after a base specifier and between digits are ignored. If there
are no digits, :exc:`ValueError` will be raised.
.. c:function:: PyObject* PyLong_FromUnicode(Py_UNICODE *u, Py_ssize_t length, int base)
Convert a sequence of Unicode digits to a Python integer value. The Unicode
string is first encoded to a byte string using :c:func:`PyUnicode_EncodeDecimal`
and then converted using :c:func:`PyLong_FromString`.
.. deprecated-removed:: 3.3 4.0
Part of the old-style :c:type:`Py_UNICODE` API; please migrate to using
:c:func:`PyLong_FromUnicodeObject`.
.. c:function:: PyObject* PyLong_FromUnicodeObject(PyObject *u, int base)
Convert a sequence of Unicode digits in the string *u* to a Python integer
value. The Unicode string is first encoded to a byte string using
:c:func:`PyUnicode_EncodeDecimal` and then converted using
:c:func:`PyLong_FromString`.
.. 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`.
.. XXX alias PyLong_AS_LONG (for now)
.. c:function:: long PyLong_AsLong(PyObject *obj)
.. index::
single: LONG_MAX
single: OverflowError (built-in exception)
Return a C :c:type:`long` representation of *obj*. If *obj* is not an
instance of :c:type:`PyLongObject`, first call its :meth:`__int__` 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:type:`long`.
Returns ``-1`` on error. Use :c:func:`PyErr_Occurred` to disambiguate.
.. c:function:: long PyLong_AsLongAndOverflow(PyObject *obj, int *overflow)
Return a C :c:type:`long` representation of *obj*. If *obj* is not an
instance of :c:type:`PyLongObject`, first call its :meth:`__int__` method
(if present) to convert it to a :c:type:`PyLongObject`.
If the value of *obj* is greater than :const:`LONG_MAX` or less than
:const:`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.
.. c:function:: long long PyLong_AsLongLong(PyObject *obj)
.. index::
single: OverflowError (built-in exception)
Return a C :c:type:`long long` representation of *obj*. If *obj* is not an
instance of :c:type:`PyLongObject`, first call its :meth:`__int__` 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:type:`long`.
Returns ``-1`` on error. Use :c:func:`PyErr_Occurred` to disambiguate.
.. c:function:: long long PyLong_AsLongLongAndOverflow(PyObject *obj, int *overflow)
Return a C :c:type:`long long` representation of *obj*. If *obj* is not an
instance of :c:type:`PyLongObject`, first call its :meth:`__int__` method
(if present) to convert it to a :c:type:`PyLongObject`.
If the value of *obj* is greater than :const:`PY_LLONG_MAX` or less than
:const:`PY_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
.. c:function:: Py_ssize_t PyLong_AsSsize_t(PyObject *pylong)
.. index::
single: PY_SSIZE_T_MAX
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
single: OverflowError (built-in exception)
Return a C :c:type:`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:type:`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
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:type:`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:type:`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:type:`unsigned long` representation of *obj*. If *obj*
is not an instance of :c:type:`PyLongObject`, first call its :meth:`__int__`
method (if present) to convert it to a :c:type:`PyLongObject`.
If the value of *obj* is out of range for an :c:type:`unsigned long`,
return the reduction of that value modulo ``ULONG_MAX + 1``.
Returns ``-1`` on error. Use :c:func:`PyErr_Occurred` to disambiguate.
.. c:function:: unsigned long long PyLong_AsUnsignedLongLongMask(PyObject *obj)
Return a C :c:type:`unsigned long long` representation of *obj*. If *obj*
is not an instance of :c:type:`PyLongObject`, first call its :meth:`__int__`
method (if present) to convert it to a :c:type:`PyLongObject`.
If the value of *obj* is out of range for an :c:type:`unsigned long long`,
return the reduction of that value modulo ``PY_ULLONG_MAX + 1``.
Returns ``-1`` on error. Use :c:func:`PyErr_Occurred` to disambiguate.
.. c:function:: double PyLong_AsDouble(PyObject *pylong)
Return a C :c:type:`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:type:`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:type:`void` pointer.
If *pylong* cannot be converted, an :exc:`OverflowError` will be raised. This
is only assured to produce a usable :c:type:`void` pointer for values created
with :c:func:`PyLong_FromVoidPtr`.
Returns *NULL* on error. Use :c:func:`PyErr_Occurred` to disambiguate.