mirror of
https://github.com/python/cpython.git
synced 2025-11-04 03:44:55 +00:00
685 lines
31 KiB
ReStructuredText
685 lines
31 KiB
ReStructuredText
.. highlightlang:: c
|
|
|
|
|
|
.. _exceptionhandling:
|
|
|
|
******************
|
|
Exception Handling
|
|
******************
|
|
|
|
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 Unix :c:data:`errno` variable:
|
|
there is a global indicator (per thread) of the last error that occurred. Most
|
|
functions don't clear this on success, but will set it to indicate the cause of
|
|
the error on failure. Most 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 :c:func:`PyArg_\*` functions return ``1`` for success and
|
|
``0`` for failure).
|
|
|
|
When a function must fail because some function it called failed, it generally
|
|
doesn't set the error indicator; the function it called already set it. It is
|
|
responsible for either handling the error and clearing the exception or
|
|
returning after cleaning up any resources it holds (such as object references or
|
|
memory allocations); it should *not* continue normally if it is not prepared to
|
|
handle the error. If returning due to an error, it is important to indicate to
|
|
the caller that an error has been set. If the error is not handled or carefully
|
|
propagated, additional calls into the Python/C API may not behave as intended
|
|
and may fail in mysterious ways.
|
|
|
|
The error indicator consists of three Python objects corresponding to the result
|
|
of ``sys.exc_info()``. API functions exist to interact with the error indicator
|
|
in various ways. There is a separate error indicator for each thread.
|
|
|
|
.. XXX Order of these should be more thoughtful.
|
|
Either alphabetical or some kind of structure.
|
|
|
|
|
|
.. c:function:: void PyErr_PrintEx(int set_sys_last_vars)
|
|
|
|
Print a standard traceback to ``sys.stderr`` and clear the error indicator.
|
|
Call this function only when the error indicator is set. (Otherwise it will
|
|
cause a fatal error!)
|
|
|
|
If *set_sys_last_vars* is nonzero, the variables :data:`sys.last_type`,
|
|
:data:`sys.last_value` and :data:`sys.last_traceback` will be set to the
|
|
type, value and traceback of the printed exception, respectively.
|
|
|
|
|
|
.. c:function:: void PyErr_Print()
|
|
|
|
Alias for ``PyErr_PrintEx(1)``.
|
|
|
|
|
|
.. c:function:: PyObject* PyErr_Occurred()
|
|
|
|
Test whether the error indicator is set. If set, return the exception *type*
|
|
(the first argument to the last call to one of the :c:func:`PyErr_Set\*`
|
|
functions or to :c:func:`PyErr_Restore`). If not set, return *NULL*. You do not
|
|
own a reference to the return value, so you do not need to :c:func:`Py_DECREF`
|
|
it.
|
|
|
|
.. note::
|
|
|
|
Do not compare the return value to a specific exception; use
|
|
:c:func:`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 the a subclass of the expected exception.)
|
|
|
|
|
|
.. c:function:: 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.
|
|
|
|
|
|
.. c:function:: int PyErr_GivenExceptionMatches(PyObject *given, PyObject *exc)
|
|
|
|
Return true if the *given* exception matches the exception 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 exceptions in the tuple (and
|
|
recursively in subtuples) are searched for a match.
|
|
|
|
|
|
.. c:function:: void PyErr_NormalizeException(PyObject**exc, PyObject**val, PyObject**tb)
|
|
|
|
Under certain circumstances, the values returned by :c:func:`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.
|
|
|
|
|
|
.. c:function:: void PyErr_Clear()
|
|
|
|
Clear the error indicator. If the error indicator is not set, there is no
|
|
effect.
|
|
|
|
|
|
.. c:function:: 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.
|
|
|
|
.. note::
|
|
|
|
This function is normally only used by code that needs to handle exceptions or
|
|
by code that needs to save and restore the error indicator temporarily.
|
|
|
|
|
|
.. c:function:: 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.)
|
|
|
|
.. note::
|
|
|
|
This function is normally only used by code that needs to save and restore the
|
|
error indicator temporarily; use :c:func:`PyErr_Fetch` to save the current
|
|
exception state.
|
|
|
|
|
|
.. c:function:: void PyErr_SetString(PyObject *type, const char *message)
|
|
|
|
This is the most common way to set the error indicator. The first argument
|
|
specifies the exception type; it is normally one of the standard exceptions,
|
|
e.g. :c:data:`PyExc_RuntimeError`. You need not increment its reference count.
|
|
The second argument is an error message; it is decoded from ``'utf-8``'.
|
|
|
|
|
|
.. c:function:: void PyErr_SetObject(PyObject *type, PyObject *value)
|
|
|
|
This function is similar to :c:func:`PyErr_SetString` but lets you specify an
|
|
arbitrary Python object for the "value" of the exception.
|
|
|
|
|
|
.. c:function:: PyObject* PyErr_Format(PyObject *exception, const char *format, ...)
|
|
|
|
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 :c:func:`PyUnicode_FromFormat`. *format* is an ASCII-encoded
|
|
string.
|
|
|
|
|
|
.. c:function:: void PyErr_SetNone(PyObject *type)
|
|
|
|
This is a shorthand for ``PyErr_SetObject(type, Py_None)``.
|
|
|
|
|
|
.. c:function:: int PyErr_BadArgument()
|
|
|
|
This is a shorthand for ``PyErr_SetString(PyExc_TypeError, message)``, where
|
|
*message* indicates that a built-in operation was invoked with an illegal
|
|
argument. It is mostly for internal use.
|
|
|
|
|
|
.. c:function:: PyObject* PyErr_NoMemory()
|
|
|
|
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.
|
|
|
|
|
|
.. c:function:: PyObject* PyErr_SetFromErrno(PyObject *type)
|
|
|
|
.. index:: single: strerror()
|
|
|
|
This is a convenience function to raise an exception when a C library function
|
|
has returned an error and set the C variable :c:data:`errno`. It constructs a
|
|
tuple object whose first item is the integer :c:data:`errno` value and whose
|
|
second item is the corresponding error message (gotten from :c:func:`strerror`),
|
|
and then calls ``PyErr_SetObject(type, object)``. On Unix, when the
|
|
:c:data:`errno` value is :const:`EINTR`, indicating an interrupted system call,
|
|
this calls :c:func:`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.
|
|
|
|
|
|
.. c:function:: PyObject* PyErr_SetFromErrnoWithFilename(PyObject *type, const char *filename)
|
|
|
|
Similar to :c:func:`PyErr_SetFromErrno`, with the additional behavior that if
|
|
*filename* is not *NULL*, it is passed to the constructor of *type* as a third
|
|
parameter. In the case of exceptions such as :exc:`IOError` and :exc:`OSError`,
|
|
this is used to define the :attr:`filename` attribute of the exception instance.
|
|
*filename* is decoded from the filesystem encoding
|
|
(:func:`sys.getfilesystemencoding`).
|
|
|
|
|
|
.. c:function:: PyObject* PyErr_SetFromWindowsErr(int ierr)
|
|
|
|
This is a convenience function to raise :exc:`WindowsError`. If called with
|
|
*ierr* of :c:data:`0`, the error code returned by a call to :c:func:`GetLastError`
|
|
is used instead. It calls the Win32 function :c:func:`FormatMessage` to retrieve
|
|
the Windows description of error code given by *ierr* or :c:func:`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
|
|
:c:func:`FormatMessage`), and then calls ``PyErr_SetObject(PyExc_WindowsError,
|
|
object)``. This function always returns *NULL*. Availability: Windows.
|
|
|
|
|
|
.. c:function:: PyObject* PyErr_SetExcFromWindowsErr(PyObject *type, int ierr)
|
|
|
|
Similar to :c:func:`PyErr_SetFromWindowsErr`, with an additional parameter
|
|
specifying the exception type to be raised. Availability: Windows.
|
|
|
|
|
|
.. c:function:: PyObject* PyErr_SetFromWindowsErrWithFilename(int ierr, const char *filename)
|
|
|
|
Similar to :c:func:`PyErr_SetFromWindowsErr`, with the additional behavior that
|
|
if *filename* is not *NULL*, it is passed to the constructor of
|
|
:exc:`WindowsError` as a third parameter. *filename* is decoded from the
|
|
filesystem encoding (:func:`sys.getfilesystemencoding`). Availability:
|
|
Windows.
|
|
|
|
|
|
.. c:function:: PyObject* PyErr_SetExcFromWindowsErrWithFilename(PyObject *type, int ierr, char *filename)
|
|
|
|
Similar to :c:func:`PyErr_SetFromWindowsErrWithFilename`, with an additional
|
|
parameter specifying the exception type to be raised. Availability: Windows.
|
|
|
|
|
|
.. c:function:: void PyErr_SyntaxLocationEx(char *filename, int lineno, int col_offset)
|
|
|
|
Set file, line, and offset information for the current exception. If the
|
|
current exception is not a :exc:`SyntaxError`, then it sets additional
|
|
attributes, which make the exception printing subsystem think the exception
|
|
is a :exc:`SyntaxError`. *filename* is decoded from the filesystem encoding
|
|
(:func:`sys.getfilesystemencoding`).
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
|
|
.. c:function:: void PyErr_SyntaxLocation(char *filename, int lineno)
|
|
|
|
Like :c:func:`PyErr_SyntaxLocationExc`, but the col_offset parameter is
|
|
omitted.
|
|
|
|
|
|
.. c:function:: void PyErr_BadInternalCall()
|
|
|
|
This is a shorthand for ``PyErr_SetString(PyExc_SystemError, message)``,
|
|
where *message* indicates that an internal operation (e.g. a Python/C API
|
|
function) was invoked with an illegal argument. It is mostly for internal
|
|
use.
|
|
|
|
|
|
.. c:function:: int PyErr_WarnEx(PyObject *category, char *message, int stack_level)
|
|
|
|
Issue a warning message. The *category* argument is a warning category (see
|
|
below) or *NULL*; the *message* argument is an 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 :c:func:`PyErr_WarnEx`, 2 is the function above that,
|
|
and so forth.
|
|
|
|
This function normally prints a warning message to *sys.stderr*; however, it is
|
|
also possible that the user has specified that warnings are to be turned into
|
|
errors, and in that case this will raise an exception. It is also possible that
|
|
the function raises an exception because of a problem with the warning machinery
|
|
(the implementation imports the :mod:`warnings` module to do the heavy lifting).
|
|
The return value is ``0`` if no exception is raised, or ``-1`` if an exception
|
|
is raised. (It is not possible to determine whether a warning message is
|
|
actually printed, nor what the reason is for the exception; this is
|
|
intentional.) If an exception is raised, the caller should do its normal
|
|
exception handling (for example, :c:func:`Py_DECREF` owned references and return
|
|
an error value).
|
|
|
|
Warning categories must be subclasses of :c:data:`Warning`; the default warning
|
|
category is :c:data:`RuntimeWarning`. The standard Python warning categories are
|
|
available as global variables whose names are ``PyExc_`` followed by the Python
|
|
exception name. These have the type :c:type:`PyObject\*`; they are all class
|
|
objects. Their names are :c:data:`PyExc_Warning`, :c:data:`PyExc_UserWarning`,
|
|
:c:data:`PyExc_UnicodeWarning`, :c:data:`PyExc_DeprecationWarning`,
|
|
:c:data:`PyExc_SyntaxWarning`, :c:data:`PyExc_RuntimeWarning`, and
|
|
:c:data:`PyExc_FutureWarning`. :c:data:`PyExc_Warning` is a subclass of
|
|
:c:data:`PyExc_Exception`; the other warning categories are subclasses of
|
|
:c:data:`PyExc_Warning`.
|
|
|
|
For information about warning control, see the documentation for the
|
|
:mod:`warnings` module and the :option:`-W` option in the command line
|
|
documentation. There is no C API for warning control.
|
|
|
|
|
|
.. c:function:: int PyErr_WarnExplicit(PyObject *category, const char *message, const char *filename, int lineno, const char *module, PyObject *registry)
|
|
|
|
Issue a warning message with explicit control over all warning attributes. This
|
|
is a straightforward wrapper around the Python function
|
|
:func:`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. *message* and *module* are UTF-8 encoded strings,
|
|
*filename* is decoded from the filesystem encoding
|
|
(:func:`sys.getfilesystemencoding`).
|
|
|
|
|
|
.. c:function:: int PyErr_WarnFormat(PyObject *category, Py_ssize_t stack_level, const char *format, ...)
|
|
|
|
Function similar to :c:func:`PyErr_WarnEx`, but use
|
|
:c:func:`PyUnicode_FromFormat` to format the warning message. *format* is
|
|
an ASCII-encoded string.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
.. c:function:: int PyErr_CheckSignals()
|
|
|
|
.. index::
|
|
module: signal
|
|
single: SIGINT
|
|
single: KeyboardInterrupt (built-in exception)
|
|
|
|
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 :mod:`signal` module is supported, this can invoke a
|
|
signal handler written in Python. In all cases, the default effect for
|
|
:const:`SIGINT` is to raise the :exc:`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.
|
|
|
|
|
|
.. c:function:: void PyErr_SetInterrupt()
|
|
|
|
.. index::
|
|
single: SIGINT
|
|
single: KeyboardInterrupt (built-in exception)
|
|
|
|
This function simulates the effect of a :const:`SIGINT` signal arriving --- the
|
|
next time :c:func:`PyErr_CheckSignals` is called, :exc:`KeyboardInterrupt` will
|
|
be raised. It may be called without holding the interpreter lock.
|
|
|
|
.. % XXX This was described as obsolete, but is used in
|
|
.. % _thread.interrupt_main() (used from IDLE), so it's still needed.
|
|
|
|
|
|
.. c:function:: int PySignal_SetWakeupFd(int fd)
|
|
|
|
This utility function specifies a file descriptor to which a ``'\0'`` byte will
|
|
be written whenever a signal is received. It returns the previous such file
|
|
descriptor. The value ``-1`` disables the feature; this is the initial state.
|
|
This is equivalent to :func:`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.
|
|
|
|
|
|
.. c:function:: PyObject* PyErr_NewException(char *name, PyObject *base, PyObject *dict)
|
|
|
|
This utility function creates and returns a new exception object. The *name*
|
|
argument must be the name of the new exception, a C string of the form
|
|
``module.class``. The *base* and *dict* arguments are normally *NULL*. This
|
|
creates a class object derived from :exc:`Exception` (accessible in C as
|
|
:c:data:`PyExc_Exception`).
|
|
|
|
The :attr:`__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.
|
|
|
|
|
|
.. c:function:: PyObject* PyErr_NewExceptionWithDoc(char *name, char *doc, PyObject *base, PyObject *dict)
|
|
|
|
Same as :c:func:`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.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
|
|
.. c:function:: void PyErr_WriteUnraisable(PyObject *obj)
|
|
|
|
This utility function prints a warning message to ``sys.stderr`` when an
|
|
exception has been set but it is impossible for the interpreter to actually
|
|
raise the exception. It is used, for example, when an exception occurs in an
|
|
:meth:`__del__` method.
|
|
|
|
The function is called with a single argument *obj* that identifies the context
|
|
in which the unraisable exception occurred. The repr of *obj* will be printed in
|
|
the warning message.
|
|
|
|
|
|
Exception Objects
|
|
=================
|
|
|
|
.. c:function:: PyObject* PyException_GetTraceback(PyObject *ex)
|
|
|
|
Return the traceback associated with the exception as a new reference, as
|
|
accessible from Python through :attr:`__traceback__`. If there is no
|
|
traceback associated, this returns *NULL*.
|
|
|
|
|
|
.. c:function:: int PyException_SetTraceback(PyObject *ex, PyObject *tb)
|
|
|
|
Set the traceback associated with the exception to *tb*. Use ``Py_None`` to
|
|
clear it.
|
|
|
|
|
|
.. c:function:: 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 :attr:`__context__`. If there is no context associated, this
|
|
returns *NULL*.
|
|
|
|
|
|
.. c:function:: 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*.
|
|
|
|
|
|
.. c:function:: PyObject* PyException_GetCause(PyObject *ex)
|
|
|
|
Return the cause (another exception instance set by ``raise ... from ...``)
|
|
associated with the exception as a new reference, as accessible from Python
|
|
through :attr:`__cause__`. If there is no cause associated, this returns
|
|
*NULL*.
|
|
|
|
|
|
.. c:function:: void PyException_SetCause(PyObject *ex, PyObject *ctx)
|
|
|
|
Set the cause 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*.
|
|
|
|
|
|
.. _unicodeexceptions:
|
|
|
|
Unicode Exception Objects
|
|
=========================
|
|
|
|
The following functions are used to create and modify Unicode exceptions from C.
|
|
|
|
.. c:function:: 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 :class:`UnicodeDecodeError` object with the attributes *encoding*,
|
|
*object*, *length*, *start*, *end* and *reason*. *encoding* and *reason* are
|
|
UTF-8 encoded strings.
|
|
|
|
.. c:function:: 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 :class:`UnicodeEncodeError` object with the attributes *encoding*,
|
|
*object*, *length*, *start*, *end* and *reason*. *encoding* and *reason* are
|
|
UTF-8 encoded strings.
|
|
|
|
.. c:function:: PyObject* PyUnicodeTranslateError_Create(const Py_UNICODE *object, Py_ssize_t length, Py_ssize_t start, Py_ssize_t end, const char *reason)
|
|
|
|
Create a :class:`UnicodeTranslateError` object with the attributes *object*,
|
|
*length*, *start*, *end* and *reason*. *reason* is an UTF-8 encoded string.
|
|
|
|
.. c:function:: PyObject* PyUnicodeDecodeError_GetEncoding(PyObject *exc)
|
|
PyObject* PyUnicodeEncodeError_GetEncoding(PyObject *exc)
|
|
|
|
Return the *encoding* attribute of the given exception object.
|
|
|
|
.. c:function:: PyObject* PyUnicodeDecodeError_GetObject(PyObject *exc)
|
|
PyObject* PyUnicodeEncodeError_GetObject(PyObject *exc)
|
|
PyObject* PyUnicodeTranslateError_GetObject(PyObject *exc)
|
|
|
|
Return the *object* attribute of the given exception object.
|
|
|
|
.. c:function:: 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.
|
|
|
|
.. c:function:: 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.
|
|
|
|
.. c:function:: 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.
|
|
|
|
.. c:function:: 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.
|
|
|
|
.. c:function:: PyObject* PyUnicodeDecodeError_GetReason(PyObject *exc)
|
|
PyObject* PyUnicodeEncodeError_GetReason(PyObject *exc)
|
|
PyObject* PyUnicodeTranslateError_GetReason(PyObject *exc)
|
|
|
|
Return the *reason* attribute of the given exception object.
|
|
|
|
.. c:function:: 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.
|
|
|
|
|
|
Recursion Control
|
|
=================
|
|
|
|
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).
|
|
|
|
.. c:function:: int Py_EnterRecursiveCall(char *where)
|
|
|
|
Marks a point where a recursive C-level call is about to be performed.
|
|
|
|
If :const:`USE_STACKCHECK` is defined, this function checks if the the OS
|
|
stack overflowed using :c:func:`PyOS_CheckStack`. In this is the case, it
|
|
sets a :exc:`MemoryError` and returns a nonzero value.
|
|
|
|
The function then checks if the recursion limit is reached. If this is the
|
|
case, a :exc:`RuntimeError` 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 :exc:`RuntimeError` message caused by the recursion depth
|
|
limit.
|
|
|
|
.. c:function:: void Py_LeaveRecursiveCall()
|
|
|
|
Ends a :c:func:`Py_EnterRecursiveCall`. Must be called once for each
|
|
*successful* invocation of :c:func:`Py_EnterRecursiveCall`.
|
|
|
|
Properly implementing :attr:`tp_repr` for container types requires
|
|
special recursion handling. In addition to protecting the stack,
|
|
:attr:`tp_repr` also needs to track objects to prevent cycles. The
|
|
following two functions facilitate this functionality. Effectively,
|
|
these are the C equivalent to :func:`reprlib.recursive_repr`.
|
|
|
|
.. c:function:: int Py_ReprEnter(PyObject *object)
|
|
|
|
Called at the beginning of the :attr:`tp_repr` implementation to
|
|
detect cycles.
|
|
|
|
If the object has already been processed, the function returns a
|
|
positive integer. In that case the :attr:`tp_repr` implementation
|
|
should return a string object indicating a cycle. As examples,
|
|
:class:`dict` objects return ``{...}`` and :class:`list` objects
|
|
return ``[...]``.
|
|
|
|
The function will return a negative integer if the recursion limit
|
|
is reached. In that case the :attr:`tp_repr` implementation should
|
|
typically return ``NULL``.
|
|
|
|
Otherwise, the function returns zero and the :attr:`tp_repr`
|
|
implementation can continue normally.
|
|
|
|
.. c:function:: void Py_ReprLeave(PyObject *object)
|
|
|
|
Ends a :c:func:`Py_ReprEnter`. Must be called once for each
|
|
invocation of :c:func:`Py_ReprEnter` that returns zero.
|
|
|
|
|
|
.. _standardexceptions:
|
|
|
|
Standard Exceptions
|
|
===================
|
|
|
|
All standard Python exceptions are available as global variables whose names are
|
|
``PyExc_`` followed by the Python exception name. These have the type
|
|
:c:type:`PyObject\*`; they are all class objects. For completeness, here are all
|
|
the variables:
|
|
|
|
+-------------------------------------+----------------------------+----------+
|
|
| C Name | Python Name | Notes |
|
|
+=====================================+============================+==========+
|
|
| :c:data:`PyExc_BaseException` | :exc:`BaseException` | \(1) |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_Exception` | :exc:`Exception` | \(1) |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_ArithmeticError` | :exc:`ArithmeticError` | \(1) |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_LookupError` | :exc:`LookupError` | \(1) |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_AssertionError` | :exc:`AssertionError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_AttributeError` | :exc:`AttributeError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_EOFError` | :exc:`EOFError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_EnvironmentError` | :exc:`EnvironmentError` | \(1) |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_FloatingPointError` | :exc:`FloatingPointError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_IOError` | :exc:`IOError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_ImportError` | :exc:`ImportError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_IndexError` | :exc:`IndexError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_KeyError` | :exc:`KeyError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_KeyboardInterrupt` | :exc:`KeyboardInterrupt` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_MemoryError` | :exc:`MemoryError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_NameError` | :exc:`NameError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_NotImplementedError` | :exc:`NotImplementedError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_OSError` | :exc:`OSError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_OverflowError` | :exc:`OverflowError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_ReferenceError` | :exc:`ReferenceError` | \(2) |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_RuntimeError` | :exc:`RuntimeError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_SyntaxError` | :exc:`SyntaxError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_SystemError` | :exc:`SystemError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_SystemExit` | :exc:`SystemExit` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_TypeError` | :exc:`TypeError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_ValueError` | :exc:`ValueError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_WindowsError` | :exc:`WindowsError` | \(3) |
|
|
+-------------------------------------+----------------------------+----------+
|
|
| :c:data:`PyExc_ZeroDivisionError` | :exc:`ZeroDivisionError` | |
|
|
+-------------------------------------+----------------------------+----------+
|
|
|
|
.. index::
|
|
single: PyExc_BaseException
|
|
single: PyExc_Exception
|
|
single: PyExc_ArithmeticError
|
|
single: PyExc_LookupError
|
|
single: PyExc_AssertionError
|
|
single: PyExc_AttributeError
|
|
single: PyExc_EOFError
|
|
single: PyExc_EnvironmentError
|
|
single: PyExc_FloatingPointError
|
|
single: PyExc_IOError
|
|
single: PyExc_ImportError
|
|
single: PyExc_IndexError
|
|
single: PyExc_KeyError
|
|
single: PyExc_KeyboardInterrupt
|
|
single: PyExc_MemoryError
|
|
single: PyExc_NameError
|
|
single: PyExc_NotImplementedError
|
|
single: PyExc_OSError
|
|
single: PyExc_OverflowError
|
|
single: PyExc_ReferenceError
|
|
single: PyExc_RuntimeError
|
|
single: PyExc_SyntaxError
|
|
single: PyExc_SystemError
|
|
single: PyExc_SystemExit
|
|
single: PyExc_TypeError
|
|
single: PyExc_ValueError
|
|
single: PyExc_WindowsError
|
|
single: PyExc_ZeroDivisionError
|
|
|
|
Notes:
|
|
|
|
(1)
|
|
This is a base class for other standard exceptions.
|
|
|
|
(2)
|
|
This is the same as :exc:`weakref.ReferenceError`.
|
|
|
|
(3)
|
|
Only defined on Windows; protect code that uses this by testing that the
|
|
preprocessor macro ``MS_WINDOWS`` is defined.
|