Manipulando Exceções

As funções descritas nesse capítulo permitem você tratar e gerar exceções em Python. É importante entender alguns princípios básicos no tratamento de exceção no Python. Funciona de forma parecida com a variável POSIX errno: existe um indicador global (por thread) do último erro ocorrido. A maioria das funções da API C não limpa isso com êxito, mas indica a causa do erro na falha. A maioria das funções da API retorna um indicador de erro, geralmente, NULL se eles devem retornar um ponteiro, or -1 se retornarem um número inteiro (exceção: as funções PyArg_*() retornam 1 em caso de sucesso e 0 em caso de falha)

Concretamente, o indicador de erro consiste em três ponteiros de objeto: o tipo da exceção, o valor da exceção e o objeto de traceback. Qualquer um desses ponteiros pode ser NULL se não definido (embora algumas combinações sejam proibidas, por exemplo, você não pode ter um retorno não NULL se o tipo de exceção for NULL).

Quando uma função deve falhar porque devido à falha de alguma função que ela chamou, ela geralmente não define o indicador de erro; a função que ela chamou já o definiu. Ela é responsável por manipular o erro e limpar a exceção ou retornar após limpar todos os recursos que possui (como referências a objetos ou alocações de memória); ela não deve continuar normalmente se não estiver preparada para lidar com o erro. Se estiver retornando devido a um erro, é importante indicar ao chamador que um erro foi definido. Se o erro não for manipulado ou propagado com cuidado, chamadas adicionais para a API Python/C podem não se comportar conforme o esperado e podem falhar de maneiras misteriosas.

Nota

O indicador de erro not é resultado de sys.exc_info(). O primeiro corresponde a uma exceção que ainda não foi capturada (e, portanto, ainda está se propagando), enquanto o segundo retorna uma exceção após ser capturada (e, portanto, parou de se propagar).

Impressão e limpeza

void PyErr_Clear()

Limpe o indicador de erro. Se o indicador de erro não estiver definido, não haverá efeito.

void PyErr_PrintEx(int set_sys_last_vars)

Print a standard traceback to sys.stderr and clear the error indicator. Unless the error is a SystemExit, in that case no traceback is printed and the Python process will exit with the error code specified by the SystemExit instance.

Chame esta função apenas quando o indicador de erro estiver definido. Caso contrário, causará um erro fatal!

If set_sys_last_vars is nonzero, the variables sys.last_type, sys.last_value and sys.last_traceback will be set to the type, value and traceback of the printed exception, respectively.

void PyErr_Print()

Apelido para PyErr_PrintEx(1).

void PyErr_WriteUnraisable(PyObject *obj)

Chama sys.unraisablehook() usando a exceção atual e o argumento 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 __del__() method.

The function is called with a single argument obj that identifies the context in which the unraisable exception occurred. If possible, the repr of obj will be printed in the warning message.

Uma exceção deve ser definida ao chamar essa função.

Lançando exceções

Essas funções ajudam a definir o indicador de erro do thread. Por conveniência, algumas dessas funções sempre retornam um ponteiro NULL ao usar instrução com return.

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. PyExc_RuntimeError. You need not increment its reference count. The second argument is an error message; it is decoded from 'utf-8’.

void PyErr_SetObject(PyObject *type, PyObject *value)

Essa função é semelhante à PyErr_SetString() mas permite especificar um objeto Python arbitrário para o valor da exceção.

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.

Igual a PyErr_Format(), mas usando o argumento va_list em vez de um número variável de argumentos.

Novo na versão 3.5.

void PyErr_SetNone(PyObject *type)

Isso é uma abreviação para PyErr_SetObject(type, Py_None).

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.

PyObject* PyErr_NoMemory()

Return value: Always NULL.

Essa é uma abreviação para PyErr_SetNone(PyExc_MemoryError); que retorna NULL  para que uma função de alocação de objeto possa escrever return PyErr_NoMemory();  quando ficar sem memória.

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)

Return value: Always NULL.

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)

Return value: Always NULL.

Similar to PyErr_SetFromErrnoWithFilenameObject(), but takes a second filename object, for raising errors when a function that takes two filenames fails.

Novo na versão 3.4.

PyObject* PyErr_SetFromErrnoWithFilename(PyObject *type, const char *filename)

Return value: Always NULL.

Similar to PyErr_SetFromErrnoWithFilenameObject(), but the filename is given as a C string. filename is decoded from the filesystem encoding (os.fsdecode()).

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.

Disponibilidade: 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.

Disponibilidade: Windows.

PyObject* PyErr_SetFromWindowsErrWithFilename(int ierr, const char *filename)

Return value: Always NULL.

Similar à PyErr_SetFromWindowsErrWithFilenameObject(), mas o nome do arquivo é dados como uma String C. O nome do arquivo é decodificado a partir do sistema de arquivos (os.fsdecode()).

Disponibilidade: Windows.

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

Return value: Always NULL.

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

Disponibilidade: Windows.

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

Return value: Always NULL.

Similar à PyErr_SetExcFromWindowsErrWithFilenameObject(), mas aceita um segundo caminho do objeto.

Disponibilidade: Windows.

Novo na versão 3.4.

PyObject* PyErr_SetExcFromWindowsErrWithFilename(PyObject *type, int ierr, const char *filename)

Return value: Always NULL.

Similar à PyErr_SetFromWindowsErrWithFilename(), com um parâmetro adicional especificando o tipo de exceção a ser gerado.

Disponibilidade: Windows.

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

Return value: Always NULL.

This is a convenience function to raise ImportError. msg will be set as the exception’s message string. name and path, both of which can be NULL, will be set as the ImportError’s respective name and path attributes.

Novo na versão 3.3.

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

Set file, line, and offset information for the current exception. If the current exception is not a SyntaxError, then it sets additional attributes, which make the exception printing subsystem think the exception is a SyntaxError.

Novo na versão 3.4.

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

Like PyErr_SyntaxLocationObject(), but filename is a byte string decoded from the filesystem encoding (os.fsdecode()).

Novo na versão 3.2.

void PyErr_SyntaxLocation(const char *filename, int lineno)

Como PyErr_SyntaxLocationEx(), mas o parâmetro col_offset é omitido.

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.

Emitindo advertências

Use these functions to issue warnings from C code. They mirror similar functions exported by the Python warnings module. They normally print 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 they will raise an exception. It is also possible that the functions raise an exception because of a problem with the warning machinery. 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, Py_DECREF() owned references and return an error value).

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.

Warning categories must be subclasses of PyExc_Warning; PyExc_Warning is a subclass of PyExc_Exception; the default warning category is PyExc_RuntimeWarning. The standard Python warning categories are available as global variables whose names are enumerated at Categorias de aviso padrão.

For information about warning control, see the documentation for the warnings module and the -W option in the command line documentation. There is no C API for warning control.

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

Return value: Always NULL.

Muito parecido com PyErr_SetImportError() mas a função permite especificar uma subclasse de ImportError para levantar uma exceção.

Novo na versão 3.6.

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.

Novo na versão 3.4.

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.

Novo na versão 3.2.

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

Function similar to PyErr_WarnFormat(), but category is ResourceWarning and it passes source to warnings.WarningMessage().

Novo na versão 3.6.

Consultando o indicador de erro

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.

Nota

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.

Nota

Esta função, normalmente, é usada apenas pelo código que precisa capturar exceções ou pelo código que precisa salvar e restaurar temporariamente o indicador de erro. Por exemplo:

{
   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.)

Nota

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.

Nota

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.

Nota

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.

Novo na versão 3.3.

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().

Nota

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.

Novo na versão 3.3.

Tratamento de sinal

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()

Simulate the effect of a SIGINT signal arriving. The next time PyErr_CheckSignals() is called, the Python signal handler for SIGINT will be called.

If SIGINT isn’t handled by Python (it was set to signal.SIG_DFL or signal.SIG_IGN), this function does nothing.

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.

O valor -1 desabilita o recurso; este é o estado inicial. Isso é equivalente à signal.set_wakeup_fd() em Python, mas sem nenhuma verificação de erro. fd deve ser um descritor de arquivo válido. A função só deve ser chamada a partir da thread principal.

Alterado na versão 3.5: No Windows, a função agora também suporta manipuladores de socket.

Classes de exceção

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.

Novo na versão 3.2.

Objeto Exceção

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)

Defina o retorno traceback (situação da pilha de execução) associado à exceção como tb. Use Py_None para limpá-lo.

PyObject* PyException_GetContext(PyObject *ex)

Return value: New reference.

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 value: New reference.

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__ para essa função é definido True , implicitamente.

Objetos de exceção Unicode

As seguintes funções são usadas para criar e modificar exceções Unicode de 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)

Return value: New reference.

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)

Return value: New reference.

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

Obsoleto desde a versão 3.3: 3.11

Py_UNICODE is deprecated since Python 3.3. Please migrate to PyObject_CallFunction(PyExc_UnicodeEncodeError, "sOnns", ...).

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

Return value: New reference.

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

Obsoleto desde a versão 3.3: 3.11

Py_UNICODE is deprecated since Python 3.3. Please migrate to PyObject_CallFunction(PyExc_UnicodeTranslateError, "Onns", ...).

PyObject* PyUnicodeDecodeError_GetEncoding(PyObject *exc)

PyObject* PyUnicodeEncodeError_GetEncoding(PyObject *exc)

Return value: New reference.

Retorna o atributo * encoding* dado no objeto da exceção.

PyObject* PyUnicodeDecodeError_GetObject(PyObject *exc)

PyObject* PyUnicodeEncodeError_GetObject(PyObject *exc)

PyObject* PyUnicodeTranslateError_GetObject(PyObject *exc)

Return value: New reference.

Retorna o atributo object dado no objeto da exceção.

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)

Obtém o atributo start do objeto da exceção coloca-o em *start. start não deve ser NULL. Retorna 0 se não der erro, -1 caso dê erro.

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)

Define o atributo start dado no objeto de exceção start. Em caso de sucesso, retorna 0, em caso de falha, retorna -1.

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)

Obtenha o atributo end dado no objeto de exceção e coloque *end. O end não deve ser NULL. Em caso de sucesso, retorna 0, em caso de falha, retorna -1.

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)

Return value: New reference.

Retorna o atributo reason dado no objeto da exceção.

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.

Controle de recursão

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)

Marca um ponto em que a chamada recursiva em nível C está prestes a ser executada.

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)

Chamado no início da implementação tp_repr para detectar ciclos.

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 [...].

A função retornará um inteiro negativo se o limite da recursão for atingido. Nesse caso a implementação tp_repr deverá, normalmente,. retornar NULL.

Caso contrário, a função retorna zero e a implementação tp_repr poderá continuar normalmente.

void Py_ReprLeave(PyObject *object)

Termina a Py_ReprEnter(). Deve ser chamado uma vez para cada chamada de Py_ReprEnter() que retorna zero.

Exceções Padrão

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:

Nome C	Nome Python	Notas
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

Novo na versão 3.3: 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 e PyExc_TimeoutError foram introduzidos seguindo a PEP 3151.

Novo na versão 3.5: PyExc_StopAsyncIteration e PyExc_RecursionError.

Novo na versão 3.6: PyExc_ModuleNotFoundError.

Esses são os aliases de compatibilidade para PyExc_OSError:

Nome C	Notas
PyExc_EnvironmentError
PyExc_IOError
PyExc_WindowsError	(3)

Alterado na versão 3.3: Esses aliases costumavam ser tipos de exceção separados.

Notas:

1. Esta é uma classe base para outras exceções padrão.

2. Defina apenas no Windows; proteja o código que usa isso testando se a macro do pré-processador MS_WINDOWS está definida.

Categorias de aviso padrão

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:

Nome C	Nome Python	Notas
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

Novo na versão 3.2: PyExc_ResourceWarning.

Notas:

1. Esta é uma classe base para outras categorias de aviso padrão.