例外處理
********

The functions described in this chapter will let you handle and raise
Python exceptions.  It is important to understand some of the basics
of Python exception handling.  It works somewhat like the POSIX
"errno" variable: there is a global indicator (per thread) of the last
error that occurred.  Most C API functions don't clear this on
success, but will set it to indicate the cause of the error on
failure.  Most C API functions also return an error indicator, usually
*NULL* if they are supposed to return a pointer, or "-1" if they
return an integer (exception: the "PyArg_*()" functions return "1" for
success and "0" for failure).

Concretely, the error indicator consists of three object pointers: the
exception's type, the exception's value, and the traceback object.
Any of those pointers can be NULL if non-set (although some
combinations are forbidden, for example you can't have a non-NULL
traceback if the exception type is NULL).

当一个函数由于它调用的某个函数失败而必须失败时，通常不会设置错误指示器
；它调用的那个函数已经设置了它。而它负责处理错误和清理异常，或在清除其
拥有的所有资源后返回（如对象应用或内存分配）。如果不准备处理异常，则*
不*应该正常地继续。如果是由于一个错误返回，那么一定要向调用者表明已经
设置了错误。如果错误没有得到处理或小心传播，对 Python/C API的其它调用
可能不会有预期的行为，并且可能会以某种神秘的方式失败。

備註:

  错误指示器 **不是** "sys.exc_info()" 的执行结果。前者对应尚未捕获的
  异常（异常还在传播），而后者在捕获异常后返回这个异常（异常已经停止传
  播）。


打印和清理
==========

void PyErr_Clear()

   清楚错误指示器。如果没有设置错误指示器，则不会有作用。

void PyErr_PrintEx(int set_sys_last_vars)

   将标准回溯打印到 "sys.stderr" 并清除错误指示器。 **除非** 错误是
   "SystemExit"，这种情况下不会打印回溯进程，且会退出 Python 进程，并
   显示 "SystemExit" 实例指定的错误代码。

   只有在错误指示器被设置时才需要调用这个函数，否则这会导致错误！

   如果 *set_sys_last_vars* 非零，则变量 "sys.last_type"，
   "sys.last_value" 和 "sys.last_traceback" 将分别设置为打印异常的类型
   ，值和回溯。

void PyErr_Print()

   "PyErr_PrintEx(1)" 的别名。

void PyErr_WriteUnraisable(PyObject *obj)

   当设置了异常，但解释器不可能实际地触发异常时，这个实用函数向
   "sys.stderr" 打印一个警告信息。例如，当 "__del__()" 方法中发生异常
   时使用这个函数。

   该函数使用单个参数 *obj* 进行调用，该参数标识发生不可触发异常的上下
   文。如果可能，*obj* 的报告将打印在警告消息中。


抛出异常
========

These functions help you set the current thread's error indicator. For
convenience, some of these functions will always return a NULL pointer
for use in a "return" statement.

void PyErr_SetString(PyObject *type, const char *message)

   这是设置错误指示器最常用的方法。第一个参数指定异常类型；它通常是标
   准异常之一，e.g. "PyExc_RuntimeError"。你不务要增加它的引用计数。第
   二个参数是错误信息，它解码自 "'utf-8'"。

void PyErr_SetObject(PyObject *type, PyObject *value)

   此函数类似于 "PyErr_SetString()"，但是允许你为异常的“值”指定任意一
   个 Python 对象。

PyObject* PyErr_Format(PyObject *exception, const char *format, ...)
    *Return value: Always NULL.*

   This function sets the error indicator and returns *NULL*.
   *exception* should be a Python exception class.  The *format* and
   subsequent parameters help format the error message; they have the
   same meaning and values as in "PyUnicode_FromFormat()". *format* is
   an ASCII-encoded string.

PyObject* PyErr_FormatV(PyObject *exception, const char *format, va_list vargs)
    *Return value: Always NULL.*

   和 "PyErr_Format()" 相同，但它接受一个 "va_list" 类型的参数而不是可
   变数量的参数集。

   3.5 版新加入.

void PyErr_SetNone(PyObject *type)

   这是 "PyErr_SetObject(type, Py_None)" 的简写。

int PyErr_BadArgument()

   这是 "PyErr_SetString(PyExc_TypeError, message)" 的简写，其中
   *message* 指出使用了非法参数调用内置操作。它主要用于内部使用。

PyObject* PyErr_NoMemory()
    *Return value: Always NULL.*

   This is a shorthand for "PyErr_SetNone(PyExc_MemoryError)"; it
   returns *NULL* so an object allocation function can write "return
   PyErr_NoMemory();" when it runs out of memory.

PyObject* PyErr_SetFromErrno(PyObject *type)
    *Return value: Always NULL.*

   This is a convenience function to raise an exception when a C
   library function has returned an error and set the C variable
   "errno".  It constructs a tuple object whose first item is the
   integer "errno" value and whose second item is the corresponding
   error message (gotten from "strerror()"), and then calls
   "PyErr_SetObject(type, object)".  On Unix, when the "errno" value
   is "EINTR", indicating an interrupted system call, this calls
   "PyErr_CheckSignals()", and if that set the error indicator, leaves
   it set to that.  The function always returns *NULL*, so a wrapper
   function around a system call can write "return
   PyErr_SetFromErrno(type);" when the system call returns an error.

PyObject* PyErr_SetFromErrnoWithFilenameObject(PyObject *type, PyObject *filenameObject)

   Similar to "PyErr_SetFromErrno()", with the additional behavior
   that if *filenameObject* is not *NULL*, it is passed to the
   constructor of *type* as a third parameter.  In the case of
   "OSError" exception, this is used to define the "filename"
   attribute of the exception instance.

PyObject* PyErr_SetFromErrnoWithFilenameObjects(PyObject *type, PyObject *filenameObject, PyObject *filenameObject2)

   类似于 "PyErr_SetFromErrnoWithFilenameObject()" ，但接受第二个文件
   名对象，用于当一个接受两个文件名的函数失败时触发错误。

   3.4 版新加入.

PyObject* PyErr_SetFromErrnoWithFilename(PyObject *type, const char *filename)
    *Return value: Always NULL.*

   类似于 "PyErr_SetFromErrnoWithFilenameObject()" ，但文件名以 C 字符
   串形式给出。 *filename* 是从文件系统编码（"os.fsdecode()"）解码出来
   的。

PyObject* PyErr_SetFromWindowsErr(int ierr)
    *Return value: Always NULL.*

   This is a convenience function to raise "WindowsError". If called
   with *ierr* of "0", the error code returned by a call to
   "GetLastError()" is used instead.  It calls the Win32 function
   "FormatMessage()" to retrieve the Windows description of error code
   given by *ierr* or "GetLastError()", then it constructs a tuple
   object whose first item is the *ierr* value and whose second item
   is the corresponding error message (gotten from "FormatMessage()"),
   and then calls "PyErr_SetObject(PyExc_WindowsError, object)". This
   function always returns *NULL*. Availability: Windows.

PyObject* PyErr_SetExcFromWindowsErr(PyObject *type, int ierr)
    *Return value: Always NULL.*

   Similar to "PyErr_SetFromWindowsErr()", with an additional
   parameter specifying the exception type to be raised. Availability:
   Windows.

PyObject* PyErr_SetFromWindowsErrWithFilename(int ierr, const char *filename)
    *Return value: Always NULL.*

   Similar to "PyErr_SetFromWindowsErrWithFilenameObject()", but the
   filename is given as a C string.  *filename* is decoded from the
   filesystem encoding ("os.fsdecode()").  Availability: Windows.

PyObject* PyErr_SetExcFromWindowsErrWithFilenameObject(PyObject *type, int ierr, PyObject *filename)

   Similar to "PyErr_SetFromWindowsErrWithFilenameObject()", with an
   additional parameter specifying the exception type to be raised.
   Availability: Windows.

PyObject* PyErr_SetExcFromWindowsErrWithFilenameObjects(PyObject *type, int ierr, PyObject *filename, PyObject *filename2)

   Similar to "PyErr_SetExcFromWindowsErrWithFilenameObject()", but
   accepts a second filename object. Availability: Windows.

   3.4 版新加入.

PyObject* PyErr_SetExcFromWindowsErrWithFilename(PyObject *type, int ierr, const char *filename)
    *Return value: Always NULL.*

   Similar to "PyErr_SetFromWindowsErrWithFilename()", with an
   additional parameter specifying the exception type to be raised.
   Availability: Windows.

PyObject* PyErr_SetImportError(PyObject *msg, PyObject *name, PyObject *path)

   这是触发 "ImportError" 的便捷函数。 *msg* 将被设为异常的消息字符串
   。 *name* 和 *path* ，（都可以为 "NULL" ），将用来被设置
   "ImportError" 对应的属性 "name" 和 "path"。

   3.3 版新加入.

void PyErr_SyntaxLocationObject(PyObject *filename, int lineno, int col_offset)

   设置当前异常的文件，行和偏移信息。如果当前异常不是 "SyntaxError" ，
   则它设置额外的属性，使异常打印子系统认为异常是 "SyntaxError"。

   3.4 版新加入.

void PyErr_SyntaxLocationEx(const char *filename, int lineno, int col_offset)

   与 "PyErr_SyntaxLocationObject()" 类似，只是 *filename* 是从文件系
   统编码（ "os.fsdecode()" ）解码出的一个字节字符串。

   3.2 版新加入.

void PyErr_SyntaxLocation(const char *filename, int lineno)

   与 "PyErr_SyntaxLocationEx()" 类似，但省略了参数 col_offset。

void PyErr_BadInternalCall()

   这是 "PyErr_SetString(PyExc_SystemError, message)" 的缩写，其中
   *message* 表示使用了非法参数调用内部操作（例如，Python/C API 函数）
   。它主要用于内部使用。


警告
====

这些函数可以从 C 代码中发出警告。它们仿照了由 Python 模块 "warnings"
导出的函数。它们通常向 *sys.stderr* 打印一条警告信息；当然，用户也有可
能已经指定将警告转换为错误，在这种情况下，它们将触发异常。也有可能由于
警告机制出现问题，使得函数触发异常。如果没有触发异常，返回值为 "0" ；
如果触发异常，返回值为 "-1"。（无法确定是否实际打印了警告信息，也无法
确定异常触发的原因。这是故意为之）。如果触发了异常，调用者应该进行正常
的异常处理（例如，"Py_DECREF()" 持有引用并返回一个错误值）。

int PyErr_WarnEx(PyObject *category, const char *message, Py_ssize_t stack_level)

   Issue a warning message.  The *category* argument is a warning
   category (see below) or *NULL*; the *message* argument is a UTF-8
   encoded string.  *stack_level* is a positive number giving a number
   of stack frames; the warning will be issued from the  currently
   executing line of code in that stack frame.  A *stack_level* of 1
   is the function calling "PyErr_WarnEx()", 2 is  the function above
   that, and so forth.

   警告类别必须是 "PyExc_Warning" 的子类， "PyExc_Warning" 是
   "PyExc_Exception" 的子类；默认警告类别是 "PyExc_RuntimeWarning" 。
   标准 Python 警告类别作为全局变量可用，所有其名称见 标准警告类别 。

   有关警告控制的信息，参见模块文档 "warnings" 和命令行文档中的 "-W"
   选项。没有用于警告控制的 C API。

PyObject* PyErr_SetImportErrorSubclass(PyObject *msg, PyObject *name, PyObject *path)

   和 "PyErr_SetImportError()" 很类似，但这个函数允许指定一个
   "ImportError" 的子类来触发。

   3.6 版新加入.

int PyErr_WarnExplicitObject(PyObject *category, PyObject *message, PyObject *filename, int lineno, PyObject *module, PyObject *registry)

   Issue a warning message with explicit control over all warning
   attributes.  This is a straightforward wrapper around the Python
   function "warnings.warn_explicit()", see there for more
   information.  The *module* and *registry* arguments may be set to
   *NULL* to get the default effect described there.

   3.4 版新加入.

int PyErr_WarnExplicit(PyObject *category, const char *message, const char *filename, int lineno, const char *module, PyObject *registry)

   Similar to "PyErr_WarnExplicitObject()" except that *message* and
   *module* are UTF-8 encoded strings, and *filename* is decoded from
   the filesystem encoding ("os.fsdecode()").

int PyErr_WarnFormat(PyObject *category, Py_ssize_t stack_level, const char *format, ...)

   Function similar to "PyErr_WarnEx()", but use
   "PyUnicode_FromFormat()" to format the warning message.  *format*
   is an ASCII-encoded string.

   3.2 版新加入.

int PyErr_ResourceWarning(PyObject *source, Py_ssize_t stack_level, const char *format, ...)

   Function similar to "PyErr_WarnFormat()", but *category* is
   "ResourceWarning" and pass *source* to "warnings.WarningMessage()".

   3.6 版新加入.


查询错误指示器
==============

PyObject* PyErr_Occurred()
    *Return value: Borrowed reference.*

   Test whether the error indicator is set.  If set, return the
   exception *type* (the first argument to the last call to one of the
   "PyErr_Set*()" functions or to "PyErr_Restore()").  If not set,
   return *NULL*.  You do not own a reference to the return value, so
   you do not need to "Py_DECREF()" it.

   備註:

     Do not compare the return value to a specific exception; use
     "PyErr_ExceptionMatches()" instead, shown below.  (The comparison
     could easily fail since the exception may be an instance instead
     of a class, in the case of a class exception, or it may be a
     subclass of the expected exception.)

int PyErr_ExceptionMatches(PyObject *exc)

   Equivalent to "PyErr_GivenExceptionMatches(PyErr_Occurred(), exc)".
   This should only be called when an exception is actually set; a
   memory access violation will occur if no exception has been raised.

int PyErr_GivenExceptionMatches(PyObject *given, PyObject *exc)

   Return true if the *given* exception matches the exception type in
   *exc*.  If *exc* is a class object, this also returns true when
   *given* is an instance of a subclass.  If *exc* is a tuple, all
   exception types in the tuple (and recursively in subtuples) are
   searched for a match.

void PyErr_Fetch(PyObject **ptype, PyObject **pvalue, PyObject **ptraceback)

   Retrieve the error indicator into three variables whose addresses
   are passed. If the error indicator is not set, set all three
   variables to *NULL*.  If it is set, it will be cleared and you own
   a reference to each object retrieved.  The value and traceback
   object may be *NULL* even when the type object is not.

   備註:

     This function is normally only used by code that needs to catch
     exceptions or by code that needs to save and restore the error
     indicator temporarily, e.g.:

        {
           PyObject *type, *value, *traceback;
           PyErr_Fetch(&type, &value, &traceback);

           /* ... code that might produce other errors ... */

           PyErr_Restore(type, value, traceback);
        }

void PyErr_Restore(PyObject *type, PyObject *value, PyObject *traceback)

   Set  the error indicator from the three objects.  If the error
   indicator is already set, it is cleared first.  If the objects are
   *NULL*, the error indicator is cleared.  Do not pass a *NULL* type
   and non-*NULL* value or traceback.  The exception type should be a
   class.  Do not pass an invalid exception type or value. (Violating
   these rules will cause subtle problems later.)  This call takes
   away a reference to each object: you must own a reference to each
   object before the call and after the call you no longer own these
   references.  (If you don't understand this, don't use this
   function.  I warned you.)

   備註:

     This function is normally only used by code that needs to save
     and restore the error indicator temporarily.  Use "PyErr_Fetch()"
     to save the current error indicator.

void PyErr_NormalizeException(PyObject**exc, PyObject**val, PyObject**tb)

   Under certain circumstances, the values returned by "PyErr_Fetch()"
   below can be "unnormalized", meaning that "*exc" is a class object
   but "*val" is not an instance of the  same class.  This function
   can be used to instantiate the class in that case.  If the values
   are already normalized, nothing happens. The delayed normalization
   is implemented to improve performance.

   備註:

     This function *does not* implicitly set the "__traceback__"
     attribute on the exception value. If setting the traceback
     appropriately is desired, the following additional snippet is
     needed:

        if (tb != NULL) {
          PyException_SetTraceback(val, tb);
        }

void PyErr_GetExcInfo(PyObject **ptype, PyObject **pvalue, PyObject **ptraceback)

   Retrieve the exception info, as known from "sys.exc_info()".  This
   refers to an exception that was *already caught*, not to an
   exception that was freshly raised.  Returns new references for the
   three objects, any of which may be *NULL*.  Does not modify the
   exception info state.

   備註:

     This function is not normally used by code that wants to handle
     exceptions. Rather, it can be used when code needs to save and
     restore the exception state temporarily.  Use
     "PyErr_SetExcInfo()" to restore or clear the exception state.

   3.3 版新加入.

void PyErr_SetExcInfo(PyObject *type, PyObject *value, PyObject *traceback)

   Set the exception info, as known from "sys.exc_info()".  This
   refers to an exception that was *already caught*, not to an
   exception that was freshly raised.  This function steals the
   references of the arguments. To clear the exception state, pass
   *NULL* for all three arguments. For general rules about the three
   arguments, see "PyErr_Restore()".

   備註:

     This function is not normally used by code that wants to handle
     exceptions. Rather, it can be used when code needs to save and
     restore the exception state temporarily.  Use
     "PyErr_GetExcInfo()" to read the exception state.

   3.3 版新加入.


信号处理
========

int PyErr_CheckSignals()

   This function interacts with Python's signal handling.  It checks
   whether a signal has been sent to the processes and if so, invokes
   the corresponding signal handler.  If the "signal" module is
   supported, this can invoke a signal handler written in Python.  In
   all cases, the default effect for "SIGINT" is to raise the
   "KeyboardInterrupt" exception.  If an exception is raised the error
   indicator is set and the function returns "-1"; otherwise the
   function returns "0".  The error indicator may or may not be
   cleared if it was previously set.

void PyErr_SetInterrupt()

   This function simulates the effect of a "SIGINT" signal arriving
   --- the next time "PyErr_CheckSignals()" is called,
   "KeyboardInterrupt" will be raised.  It may be called without
   holding the interpreter lock.

int PySignal_SetWakeupFd(int fd)

   This utility function specifies a file descriptor to which the
   signal number is written as a single byte whenever a signal is
   received. *fd* must be non-blocking. It returns the previous such
   file descriptor.

   The value "-1" disables the feature; this is the initial state.
   This is equivalent to "signal.set_wakeup_fd()" in Python, but
   without any error checking.  *fd* should be a valid file
   descriptor.  The function should only be called from the main
   thread.

   3.5 版更變: 在 Windows 上，此函数现在也支持套接字处理。


异常类
======

PyObject* PyErr_NewException(const char *name, PyObject *base, PyObject *dict)
    *Return value: New reference.*

   This utility function creates and returns a new exception class.
   The *name* argument must be the name of the new exception, a C
   string of the form "module.classname".  The *base* and *dict*
   arguments are normally *NULL*. This creates a class object derived
   from "Exception" (accessible in C as "PyExc_Exception").

   The "__module__" attribute of the new class is set to the first
   part (up to the last dot) of the *name* argument, and the class
   name is set to the last part (after the last dot).  The *base*
   argument can be used to specify alternate base classes; it can
   either be only one class or a tuple of classes. The *dict* argument
   can be used to specify a dictionary of class variables and methods.

PyObject* PyErr_NewExceptionWithDoc(const char *name, const char *doc, PyObject *base, PyObject *dict)
    *Return value: New reference.*

   Same as "PyErr_NewException()", except that the new exception class
   can easily be given a docstring: If *doc* is non-*NULL*, it will be
   used as the docstring for the exception class.

   3.2 版新加入.


异常对象
========

PyObject* PyException_GetTraceback(PyObject *ex)
    *Return value: New reference.*

   Return the traceback associated with the exception as a new
   reference, as accessible from Python through "__traceback__".  If
   there is no traceback associated, this returns *NULL*.

int PyException_SetTraceback(PyObject *ex, PyObject *tb)

   将异常关联的回溯设置为 *tb* 。使用``Py_None``清除它。

PyObject* PyException_GetContext(PyObject *ex)

   Return the context (another exception instance during whose
   handling *ex* was raised) associated with the exception as a new
   reference, as accessible from Python through "__context__".  If
   there is no context associated, this returns *NULL*.

void PyException_SetContext(PyObject *ex, PyObject *ctx)

   Set the context associated with the exception to *ctx*.  Use *NULL*
   to clear it.  There is no type check to make sure that *ctx* is an
   exception instance. This steals a reference to *ctx*.

PyObject* PyException_GetCause(PyObject *ex)

   Return the cause (either an exception instance, or "None", set by
   "raise ... from ...") associated with the exception as a new
   reference, as accessible from Python through "__cause__".

void PyException_SetCause(PyObject *ex, PyObject *cause)

   Set the cause associated with the exception to *cause*.  Use *NULL*
   to clear it.  There is no type check to make sure that *cause* is
   either an exception instance or "None".  This steals a reference to
   *cause*.

   "__suppress_context__" is implicitly set to "True" by this
   function.


Unicode 异常对象
================

The following functions are used to create and modify Unicode
exceptions from C.

PyObject* PyUnicodeDecodeError_Create(const char *encoding, const char *object, Py_ssize_t length, Py_ssize_t start, Py_ssize_t end, const char *reason)

   Create a "UnicodeDecodeError" object with the attributes
   *encoding*, *object*, *length*, *start*, *end* and *reason*.
   *encoding* and *reason* are UTF-8 encoded strings.

PyObject* PyUnicodeEncodeError_Create(const char *encoding, const Py_UNICODE *object, Py_ssize_t length, Py_ssize_t start, Py_ssize_t end, const char *reason)

   Create a "UnicodeEncodeError" object with the attributes
   *encoding*, *object*, *length*, *start*, *end* and *reason*.
   *encoding* and *reason* are UTF-8 encoded strings.

PyObject* PyUnicodeTranslateError_Create(const Py_UNICODE *object, Py_ssize_t length, Py_ssize_t start, Py_ssize_t end, const char *reason)

   Create a "UnicodeTranslateError" object with the attributes
   *object*, *length*, *start*, *end* and *reason*. *reason* is a
   UTF-8 encoded string.

PyObject* PyUnicodeDecodeError_GetEncoding(PyObject *exc)
PyObject* PyUnicodeEncodeError_GetEncoding(PyObject *exc)

   返回给定异常对象的 *encoding* 属性

PyObject* PyUnicodeDecodeError_GetObject(PyObject *exc)
PyObject* PyUnicodeEncodeError_GetObject(PyObject *exc)
PyObject* PyUnicodeTranslateError_GetObject(PyObject *exc)

   返回给定异常对象的 *object* 属性

int PyUnicodeDecodeError_GetStart(PyObject *exc, Py_ssize_t *start)
int PyUnicodeEncodeError_GetStart(PyObject *exc, Py_ssize_t *start)
int PyUnicodeTranslateError_GetStart(PyObject *exc, Py_ssize_t *start)

   Get the *start* attribute of the given exception object and place
   it into **start*.  *start* must not be *NULL*.  Return "0" on
   success, "-1" on failure.

int PyUnicodeDecodeError_SetStart(PyObject *exc, Py_ssize_t start)
int PyUnicodeEncodeError_SetStart(PyObject *exc, Py_ssize_t start)
int PyUnicodeTranslateError_SetStart(PyObject *exc, Py_ssize_t start)

   Set the *start* attribute of the given exception object to *start*.
   Return "0" on success, "-1" on failure.

int PyUnicodeDecodeError_GetEnd(PyObject *exc, Py_ssize_t *end)
int PyUnicodeEncodeError_GetEnd(PyObject *exc, Py_ssize_t *end)
int PyUnicodeTranslateError_GetEnd(PyObject *exc, Py_ssize_t *end)

   Get the *end* attribute of the given exception object and place it
   into **end*.  *end* must not be *NULL*.  Return "0" on success,
   "-1" on failure.

int PyUnicodeDecodeError_SetEnd(PyObject *exc, Py_ssize_t end)
int PyUnicodeEncodeError_SetEnd(PyObject *exc, Py_ssize_t end)
int PyUnicodeTranslateError_SetEnd(PyObject *exc, Py_ssize_t end)

   Set the *end* attribute of the given exception object to *end*.
   Return "0" on success, "-1" on failure.

PyObject* PyUnicodeDecodeError_GetReason(PyObject *exc)
PyObject* PyUnicodeEncodeError_GetReason(PyObject *exc)
PyObject* PyUnicodeTranslateError_GetReason(PyObject *exc)

   返回给定异常对象的 *reason* 属性

int PyUnicodeDecodeError_SetReason(PyObject *exc, const char *reason)
int PyUnicodeEncodeError_SetReason(PyObject *exc, const char *reason)
int PyUnicodeTranslateError_SetReason(PyObject *exc, const char *reason)

   Set the *reason* attribute of the given exception object to
   *reason*.  Return "0" on success, "-1" on failure.


递归控制
========

These two functions provide a way to perform safe recursive calls at
the C level, both in the core and in extension modules.  They are
needed if the recursive code does not necessarily invoke Python code
(which tracks its recursion depth automatically).

int Py_EnterRecursiveCall(const char *where)

   Marks a point where a recursive C-level call is about to be
   performed.

   If "USE_STACKCHECK" is defined, this function checks if the OS
   stack overflowed using "PyOS_CheckStack()".  In this is the case,
   it sets a "MemoryError" and returns a nonzero value.

   The function then checks if the recursion limit is reached.  If
   this is the case, a "RecursionError" is set and a nonzero value is
   returned. Otherwise, zero is returned.

   *where* should be a string such as "" in instance check"" to be
   concatenated to the "RecursionError" message caused by the
   recursion depth limit.

void Py_LeaveRecursiveCall()

   Ends a "Py_EnterRecursiveCall()".  Must be called once for each
   *successful* invocation of "Py_EnterRecursiveCall()".

Properly implementing "tp_repr" for container types requires special
recursion handling.  In addition to protecting the stack, "tp_repr"
also needs to track objects to prevent cycles.  The following two
functions facilitate this functionality.  Effectively, these are the C
equivalent to "reprlib.recursive_repr()".

int Py_ReprEnter(PyObject *object)

   Called at the beginning of the "tp_repr" implementation to detect
   cycles.

   If the object has already been processed, the function returns a
   positive integer.  In that case the "tp_repr" implementation should
   return a string object indicating a cycle.  As examples, "dict"
   objects return "{...}" and "list" objects return "[...]".

   The function will return a negative integer if the recursion limit
   is reached.  In that case the "tp_repr" implementation should
   typically return "NULL".

   Otherwise, the function returns zero and the "tp_repr"
   implementation can continue normally.

void Py_ReprLeave(PyObject *object)

   Ends a "Py_ReprEnter()".  Must be called once for each invocation
   of "Py_ReprEnter()" that returns zero.


标准异常
========

All standard Python exceptions are available as global variables whose
names are "PyExc_" followed by the Python exception name.  These have
the type "PyObject*"; they are all class objects.  For completeness,
here are all the variables:

+-------------------------------------------+-----------------------------------+------------+
| C 名称                                    | Python 名称                       | 註解       |
|===========================================|===================================|============|
| "PyExc_BaseException"                     | "BaseException"                   | (1)        |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_Exception"                         | "Exception"                       | (1)        |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_ArithmeticError"                   | "ArithmeticError"                 | (1)        |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_AssertionError"                    | "AssertionError"                  |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_AttributeError"                    | "AttributeError"                  |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_BlockingIOError"                   | "BlockingIOError"                 |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_BrokenPipeError"                   | "BrokenPipeError"                 |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_BufferError"                       | "BufferError"                     |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_ChildProcessError"                 | "ChildProcessError"               |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_ConnectionAbortedError"            | "ConnectionAbortedError"          |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_ConnectionError"                   | "ConnectionError"                 |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_ConnectionRefusedError"            | "ConnectionRefusedError"          |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_ConnectionResetError"              | "ConnectionResetError"            |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_EOFError"                          | "EOFError"                        |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_FileExistsError"                   | "FileExistsError"                 |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_FileNotFoundError"                 | "FileNotFoundError"               |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_FloatingPointError"                | "FloatingPointError"              |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_GeneratorExit"                     | "GeneratorExit"                   |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_ImportError"                       | "ImportError"                     |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_IndentationError"                  | "IndentationError"                |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_IndexError"                        | "IndexError"                      |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_InterruptedError"                  | "InterruptedError"                |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_IsADirectoryError"                 | "IsADirectoryError"               |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_KeyError"                          | "KeyError"                        |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_KeyboardInterrupt"                 | "KeyboardInterrupt"               |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_LookupError"                       | "LookupError"                     | (1)        |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_MemoryError"                       | "MemoryError"                     |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_ModuleNotFoundError"               | "ModuleNotFoundError"             |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_NameError"                         | "NameError"                       |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_NotADirectoryError"                | "NotADirectoryError"              |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_NotImplementedError"               | "NotImplementedError"             |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_OSError"                           | "OSError"                         | (1)        |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_OverflowError"                     | "OverflowError"                   |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_PermissionError"                   | "PermissionError"                 |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_ProcessLookupError"                | "ProcessLookupError"              |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_RecursionError"                    | "RecursionError"                  |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_ReferenceError"                    | "ReferenceError"                  | (2)        |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_RuntimeError"                      | "RuntimeError"                    |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_StopAsyncIteration"                | "StopAsyncIteration"              |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_StopIteration"                     | "StopIteration"                   |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_SyntaxError"                       | "SyntaxError"                     |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_SystemError"                       | "SystemError"                     |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_SystemExit"                        | "SystemExit"                      |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_TabError"                          | "TabError"                        |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_TimeoutError"                      | "TimeoutError"                    |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_TypeError"                         | "TypeError"                       |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_UnboundLocalError"                 | "UnboundLocalError"               |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_UnicodeDecodeError"                | "UnicodeDecodeError"              |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_UnicodeEncodeError"                | "UnicodeEncodeError"              |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_UnicodeError"                      | "UnicodeError"                    |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_UnicodeTranslateError"             | "UnicodeTranslateError"           |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_ValueError"                        | "ValueError"                      |            |
+-------------------------------------------+-----------------------------------+------------+
| "PyExc_ZeroDivisionError"                 | "ZeroDivisionError"               |            |
+-------------------------------------------+-----------------------------------+------------+

3.3 版新加入: "PyExc_BlockingIOError", "PyExc_BrokenPipeError",
"PyExc_ChildProcessError", "PyExc_ConnectionError",
"PyExc_ConnectionAbortedError", "PyExc_ConnectionRefusedError",
"PyExc_ConnectionResetError", "PyExc_FileExistsError",
"PyExc_FileNotFoundError", "PyExc_InterruptedError",
"PyExc_IsADirectoryError", "PyExc_NotADirectoryError",
"PyExc_PermissionError", "PyExc_ProcessLookupError" and
"PyExc_TimeoutError" 介绍如下 **PEP 3151**.

3.5 版新加入: "PyExc_StopAsyncIteration" 和 "PyExc_RecursionError".

3.6 版新加入: "PyExc_ModuleNotFoundError".

这些是兼容性别名 "PyExc_OSError":

+---------------------------------------+------------+
| C 名称                                | 註解       |
|=======================================|============|
| "PyExc_EnvironmentError"              |            |
+---------------------------------------+------------+
| "PyExc_IOError"                       |            |
+---------------------------------------+------------+
| "PyExc_WindowsError"                  | (3)        |
+---------------------------------------+------------+

3.3 版更變: 这些别名曾经是单独的异常类型。

註解：

1. 这是其他标准异常的基类。

2. This is the same as "weakref.ReferenceError".

3. Only defined on Windows; protect code that uses this by testing
   that the preprocessor macro "MS_WINDOWS" is defined.


标准警告类别
============

All standard Python warning categories are available as global
variables whose names are "PyExc_" followed by the Python exception
name. These have the type "PyObject*"; they are all class objects. For
completeness, here are all the variables:

+--------------------------------------------+-----------------------------------+------------+
| C 名称                                     | Python 名称                       | 註解       |
|============================================|===================================|============|
| "PyExc_Warning"                            | "Warning"                         | (1)        |
+--------------------------------------------+-----------------------------------+------------+
| "PyExc_BytesWarning"                       | "BytesWarning"                    |            |
+--------------------------------------------+-----------------------------------+------------+
| "PyExc_DeprecationWarning"                 | "DeprecationWarning"              |            |
+--------------------------------------------+-----------------------------------+------------+
| "PyExc_FutureWarning"                      | "FutureWarning"                   |            |
+--------------------------------------------+-----------------------------------+------------+
| "PyExc_ImportWarning"                      | "ImportWarning"                   |            |
+--------------------------------------------+-----------------------------------+------------+
| "PyExc_PendingDeprecationWarning"          | "PendingDeprecationWarning"       |            |
+--------------------------------------------+-----------------------------------+------------+
| "PyExc_ResourceWarning"                    | "ResourceWarning"                 |            |
+--------------------------------------------+-----------------------------------+------------+
| "PyExc_RuntimeWarning"                     | "RuntimeWarning"                  |            |
+--------------------------------------------+-----------------------------------+------------+
| "PyExc_SyntaxWarning"                      | "SyntaxWarning"                   |            |
+--------------------------------------------+-----------------------------------+------------+
| "PyExc_UnicodeWarning"                     | "UnicodeWarning"                  |            |
+--------------------------------------------+-----------------------------------+------------+
| "PyExc_UserWarning"                        | "UserWarning"                     |            |
+--------------------------------------------+-----------------------------------+------------+

3.2 版新加入: "PyExc_ResourceWarning".

註解：

1. 这是其他标准警告类别的基类。
