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).
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.
Note
The error indicator is not the result of
. The former corresponds to an exception that is not yet caught (and is therefore still propagating), while the latter returns an exception after it is caught (and has therefore stopped propagating).
Printing and clearing
voidPyErr_Clear()
Part of the
.Clear the error indicator. If the error indicator is not set, there is no effect.
voidPyErr_PrintEx(intset_sys_last_vars)
Part of the
.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.
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 variable
is set to the printed exception. For backwards compatibility, the deprecated variables
,
and
are also set to the type, value and traceback of this exception, respectively.
Changed in version 3.12: The setting of
was added.
voidPyErr_Print()
Part of the
.Alias for PyErr_PrintEx(1).
voidPyErr_WriteUnraisable(
*obj)
Part of the
.Call
using the current exception and obj argument.
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
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. If obj is NULL, only the traceback is printed.
An exception must be set when calling this function.
Changed in version 3.4: Print a traceback. Print only traceback if obj is NULL.
voidPyErr_FormatUnraisable(constchar*format, ...)
Similar to
, but the format and subsequent parameters help format the warning message; they have the same meaning and values as in
. PyErr_WriteUnraisable(obj) is roughly equivalent to PyErr_FormatUnraisable("Exceptionignoredin:%R",obj). If format is NULL, only the traceback is printed.
Added in version 3.13.
voidPyErr_DisplayException(
*exc)
Part of the
since version 3.12.Print the standard traceback display of exc to sys.stderr, including chained exceptions and notes.
Added in version 3.12.
voidPyErr_Display(
*unused,
*value,
*tb)
Part of the
.Legacy variant of
.
Print the exception value with its traceback to
. If value has no traceback set, tb is used as its traceback. The first argument is ignored.
If
is None, nothing is printed. If sys.stderr is not set, the exception is dumped to the C stderr stream instead.
Deprecated since version 3.12: Use
instead.
Raising exceptions
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.
voidPyErr_SetString(
*type, constchar*message)
Part of the
.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.
. You need not create a new
to it (e.g. with
). The second argument is an error message; it is decoded from 'utf-8'.
voidPyErr_SetObject(
*type,
*value)
Part of the
.This function is similar to
but lets you specify an arbitrary Python object for the “value” of the exception.
*PyErr_Format(
*exception, constchar*format, ...)
Return value: Always NULL. Part of the
.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
. format is an ASCII-encoded string.
*PyErr_FormatV(
*exception, constchar*format, va_listvargs)
Return value: Always NULL. Part of the
since version 3.5.Same as
, but taking a va_list argument rather than a variable number of arguments.
Added in version 3.5.
voidPyErr_SetNone(
*type)
Part of the
.This is a shorthand for PyErr_SetObject(type,Py_None).
intPyErr_BadArgument()
Part of the
.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.
*PyErr_NoMemory()
Return value: Always NULL. Part of the
.This is a shorthand for PyErr_SetNone(PyExc_MemoryError); it returns NULL so an object allocation function can write returnPyErr_NoMemory(); when it runs out of memory.
*PyErr_SetFromErrno(
*type)
Return value: Always NULL. Part of the
.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
, 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 returnPyErr_SetFromErrno(type); when the system call returns an error.
*PyErr_SetFromErrnoWithFilenameObject(
*type,
*filenameObject)
Return value: Always NULL. Part of the
.Similar to
, 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
exception, this is used to define the filename attribute of the exception instance.
*PyErr_SetFromErrnoWithFilenameObjects(
*type,
*filenameObject,
*filenameObject2)
Return value: Always NULL. Part of the
since version 3.7.Similar to
PyErr_SetFromErrnoWithFilenameObject()
, but takes a second filename object, for raising errors when a function that takes two filenames fails.
Added in version 3.4.
*PyErr_SetFromErrnoWithFilename(
*type, constchar*filename)
Return value: Always NULL. Part of the
.Similar to
PyErr_SetFromErrnoWithFilenameObject()
, but the filename is given as a C string. filename is decoded from the
filesystem encoding and error handler
.
*PyErr_SetFromWindowsErr(intierr)
Return value: Always NULL. Part of the
on Windows since version 3.7.This is a convenience function to raise
. 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 OSError object with the
attribute set to the error code, the
attribute set to the corresponding error message (gotten from FormatMessage()), and then calls PyErr_SetObject(PyExc_OSError,object). This function always returns NULL.
*PyErr_SetExcFromWindowsErr(
*type, intierr)
Return value: Always NULL. Part of the
on Windows since version 3.7.Similar to
, with an additional parameter specifying the exception type to be raised.
*PyErr_SetFromWindowsErrWithFilename(intierr, constchar*filename)
Return value: Always NULL. Part of the
on Windows since version 3.7.Similar to
, with the additional behavior that if filename is not NULL, it is decoded from the filesystem encoding (
) and passed to the constructor of
as a third parameter to be used to define the filename attribute of the exception instance.
*PyErr_SetExcFromWindowsErrWithFilenameObject(
*type, intierr,
*filename)
Return value: Always NULL. Part of the
on Windows since version 3.7.Similar to
, with the additional behavior that if filename is not NULL, it is passed to the constructor of
as a third parameter to be used to define the filename attribute of the exception instance.
*PyErr_SetExcFromWindowsErrWithFilenameObjects(
*type, intierr,
*filename,
*filename2)
Return value: Always NULL. Part of the
on Windows since version 3.7.Similar to
PyErr_SetExcFromWindowsErrWithFilenameObject()
, but accepts a second filename object.
Added in version 3.4.
*PyErr_SetExcFromWindowsErrWithFilename(
*type, intierr, constchar*filename)
Return value: Always NULL. Part of the
on Windows since version 3.7.Similar to
PyErr_SetFromWindowsErrWithFilename()
, with an additional parameter specifying the exception type to be raised.
*PyErr_SetImportError(
*msg,
*name,
*path)
Return value: Always NULL. Part of the
since version 3.7.This is a convenience function to raise
. 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.
Added in version 3.3.
*PyErr_SetImportErrorSubclass(
*exception,
*msg,
*name,
*path)
Return value: Always NULL. Part of the
since version 3.6.Much like
but this function allows for specifying a subclass of
to raise.
Added in version 3.6.
voidPyErr_SyntaxLocationObject(
*filename, intlineno, intcol_offset)
Set file, line, and offset information for the current exception. If the current exception is not a
, then it sets additional attributes, which make the exception printing subsystem think the exception is a SyntaxError.
Added in version 3.4.
voidPyErr_RangedSyntaxLocationObject(
*filename, intlineno, intcol_offset, intend_lineno, intend_col_offset)
Similar to
, but also sets the end_lineno and end_col_offset information for the current exception.
Added in version 3.10.
voidPyErr_SyntaxLocationEx(constchar*filename, intlineno, intcol_offset)
Part of the
since version 3.7.Like
, but filename is a byte string decoded from the
filesystem encoding and error handler
.
Added in version 3.2.
voidPyErr_SyntaxLocation(constchar*filename, intlineno)
Part of the
.Like
, but the col_offset parameter is omitted.
voidPyErr_BadInternalCall()
Part of the
.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.
*PyErr_ProgramTextObject(
*filename, intlineno)
Get the source line in filename at line lineno. filename should be a Python
object.
On success, this function returns a Python string object with the found line. On failure, this function returns NULL without an exception set.
*PyErr_ProgramText(constchar*filename, intlineno)
Part of the
.Similar to
, but filename is a constchar*, which is decoded with the
filesystem encoding and error handler
, instead of a Python object reference.
Issuing warnings
Use these functions to issue warnings from C code. They mirror similar functions exported by the Python
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,
owned references and return an error value).
intPyErr_WarnEx(
*category, constchar*message,
stack_level)
Part of the
.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
, 2 is the function above that, and so forth.
Warning categories must be subclasses of
; PyExc_Warning is a subclass of
; the default warning category is
. The standard Python warning categories are available as global variables whose names are enumerated at
.
For information about warning control, see the documentation for the
module and the
option in the command line documentation. There is no C API for warning control.
intPyErr_WarnExplicitObject(
*category,
*message,
*filename, intlineno,
*module,
*registry)
Issue a warning message with explicit control over all warning attributes. This is a straightforward wrapper around the Python function
; see there for more information. The module and registry arguments may be set to NULL to get the default effect described there.
Added in version 3.4.
intPyErr_WarnExplicit(
*category, constchar*message, constchar*filename, intlineno, constchar*module,
*registry)
Part of the
.Similar to
except that message and module are UTF-8 encoded strings, and filename is decoded from the
filesystem encoding and error handler
.
intPyErr_WarnFormat(
*category,
stack_level, constchar*format, ...)
Part of the
.Function similar to
, but uses
to format the warning message. format is an ASCII-encoded string.
Added in version 3.2.
intPyErr_WarnExplicitFormat(
*category, constchar*filename, intlineno, constchar*module,
*registry, constchar*format, ...)
Similar to
, but uses
to format the warning message. format is an ASCII-encoded string.
Added in version 3.2.
intPyErr_ResourceWarning(
*source,
stack_level, constchar*format, ...)
Part of the
since version 3.6.Function similar to
, but category is
and it passes source to warnings.WarningMessage.
Added in version 3.6.
Querying the error indicator
*PyErr_Occurred()
Return value: Borrowed reference. Part of the
.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
). If not set, return NULL. You do not own a reference to the return value, so you do not need to
it.
The caller must have an
.
Note
Do not compare the return value to a specific exception; use
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.)
intPyErr_ExceptionMatches(
*exc)
Part of the
.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.
intPyErr_GivenExceptionMatches(
*given,
*exc)
Part of the
.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.
*PyErr_GetRaisedException(void)
Return value: New reference. Part of the
since version 3.12.Return the exception currently being raised, clearing the error indicator at the same time. Return NULL if the error indicator is not set.
This function is used by code that needs to catch exceptions, or code that needs to save and restore the error indicator temporarily.
For example:
{PyObject*exc=PyErr_GetRaisedException();/* ... code that might produce other errors ... */PyErr_SetRaisedException(exc);}See also
, to save the exception currently being handled.
Added in version 3.12.
voidPyErr_SetRaisedException(
*exc)
Part of the
since version 3.12.Set exc as the exception currently being raised, clearing the existing exception if one is set. If exc is NULL, just clear the existing exception.
exc must be a valid exception or NULL.
This call “
” a reference to exc.
Added in version 3.12.
voidPyErr_Fetch(
**ptype,
**pvalue,
**ptraceback)
Part of the
.Deprecated since version 3.12: Use
instead.
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 legacy code that needs to catch exceptions or save and restore the error indicator temporarily.
For example:
{PyObject*type,*value,*traceback;PyErr_Fetch(&type,&value,&traceback);/* ... code that might produce other errors ... */PyErr_Restore(type,value,traceback);}voidPyErr_Restore(
*type,
*value,
*traceback)
Part of the
.Deprecated since version 3.12: Use
instead.
Set the error indicator from the three objects, type, value, and traceback, clearing the existing exception if one is set. 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 legacy code that needs to save and restore the error indicator temporarily. Use
to save the current error indicator.
voidPyErr_NormalizeException(
**exc,
**val,
**tb)
Part of the
.Deprecated since version 3.12: Use
instead, to avoid any possible de-normalization.
Under certain circumstances, the values returned by
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.
Note
This function does not implicitly set the
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);}
*PyErr_GetHandledException(void)
Part of the
since version 3.11.Retrieve the active exception instance, as would be returned by
. This refers to an exception that was already caught, not to an exception that was freshly raised. Returns a new reference to the exception or NULL. Does not modify the interpreter’s exception state.
Note
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
to restore or clear the exception state.
Added in version 3.11.
voidPyErr_SetHandledException(
*exc)
Part of the
since version 3.11.Set the active exception, as known from sys.exception(). This refers to an exception that was already caught, not to an exception that was freshly raised. To clear the exception state, pass NULL.
Note
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
to get the exception state.
Added in version 3.11.
voidPyErr_GetExcInfo(
**ptype,
**pvalue,
**ptraceback)
Part of the
since version 3.7.Retrieve the old-style representation of the exception info, as known from
. 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. This function is kept for backwards compatibility. Prefer using
.
Note
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
to restore or clear the exception state.
Added in version 3.3.
voidPyErr_SetExcInfo(
*type,
*value,
*traceback)
Part of the
since version 3.7.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 “
” the references of the arguments. To clear the exception state, pass NULL for all three arguments. This function is kept for backwards compatibility. Prefer using
.
Note
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
to read the exception state.
Added in version 3.3.
Changed in version 3.11: The type and traceback arguments are no longer used and can be NULL. The interpreter now derives them from the exception instance (the value argument). The function still “
” references of all three arguments.
Signal Handling
intPyErr_CheckSignals()
Part of the
.Handle external interruptions, such as signals or activating a debugger, whose processing has been delayed until it is safe to run Python code and/or raise exceptions.
For example, pressing Ctrl-C causes a terminal to send the
signal. This function executes the corresponding Python signal handler, which, by default, raises the
exception.
PyErr_CheckSignals() should be called by long-running C code frequently enough so that the response appears immediate to humans.
Handlers invoked by this function currently include:
Signal handlers, including Python functions registered using the
module.
Signal handlers are only run in the main thread of the main interpreter.
(This is where the function got the name: originally, signals were the only way to interrupt the interpreter.)
Running the garbage collector, if necessary.
Executing a pending
script.
Raise the exception set by
.
If any handler raises an exception, immediately return -1 with that exception set. Any remaining interruptions are left to be processed on the next
invocation, if appropriate.
If all handlers finish successfully, or there are no handlers to run, return 0.
Changed in version 3.12: This function may now invoke the garbage collector.
Changed in version 3.14: This function may now execute a remote debugger script, if remote debugging is enabled.
voidPyErr_SetInterrupt()
Part of the
.Simulate the effect of a SIGINT signal arriving. This is equivalent to PyErr_SetInterruptEx(SIGINT).
Note
This function is async-signal-safe. It can be called without an
and from a C signal handler.
intPyErr_SetInterruptEx(intsignum)
Part of the
since version 3.10.Simulate the effect of a signal arriving. The next time
is called, the Python signal handler for the given signal number will be called.
This function can be called by C code that sets up its own signal handling and wants Python signal handlers to be invoked as expected when an interruption is requested (for example when the user presses Ctrl-C to interrupt an operation).
If the given signal isn’t handled by Python (it was set to
or
), it will be ignored.
If signum is outside of the allowed range of signal numbers, -1 is returned. Otherwise, 0 is returned. The error indicator is never changed by this function.
Note
This function is async-signal-safe. It can be called without an
and from a C signal handler.
Added in version 3.10.
intPySignal_SetWakeupFd(intfd)
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
in Python, but without any error checking. fd should be a valid file descriptor. The function should only be called from the main thread.
Changed in version 3.5: On Windows, the function now also supports socket handles.
Exception Classes
*PyErr_NewException(constchar*name,
*base,
*dict)
Return value: New reference. Part of the
.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
(accessible in C as
).
The
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.
*PyErr_NewExceptionWithDoc(constchar*name, constchar*doc,
*base,
*dict)
Return value: New reference. Part of the
.Same as
, 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.
Added in version 3.2.
intPyExceptionClass_Check(
*ob)
Return non-zero if ob is an exception class, zero otherwise. This function always succeeds.
constchar*PyExceptionClass_Name(
*ob)
Part of the
since version 3.8.Return
of the exception class ob.
PyException_HEAD
This is a macro including the base fields for an exception object.
This was included in Python’s C API by mistake and is not designed for use in extensions. For creating custom exception objects, use
or otherwise create a class inheriting from
.
Exception Objects
intPyExceptionInstance_Check(
*op)
Return true if op is an instance of
, false otherwise. This function always succeeds.
PyExceptionInstance_Class(op)
Equivalent to
.
*PyException_GetTraceback(
*ex)
Return value: New reference. Part of the
.Return the traceback associated with the exception as a new reference, as accessible from Python through the
attribute. If there is no traceback associated, this returns NULL.
intPyException_SetTraceback(
*ex,
*tb)
Part of the
.Set the traceback associated with the exception to tb. Use Py_None to clear it.
*PyException_GetContext(
*ex)
Return value: New reference. Part of the
.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 the
attribute. If there is no context associated, this returns NULL.
voidPyException_SetContext(
*ex,
*ctx)
Part of the
.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 “
” a reference to ctx.
*PyException_GetCause(
*ex)
Return value: New reference. Part of the
.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 the
attribute.
voidPyException_SetCause(
*ex,
*cause)
Part of the
.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 “
” a reference to cause.
The
attribute is implicitly set to True by this function.
*PyException_GetArgs(
*ex)
Return value: New reference. Part of the
since version 3.12.Return
of exception ex.
voidPyException_SetArgs(
*ex,
*args)
Part of the
since version 3.12.Set
of exception ex to args.
*PyUnstable_Exc_PrepReraiseStar(
*orig,
*excs)
This is
. It may change without warning in minor releases.
Implement part of the interpreter’s implementation of except*. orig is the original exception that was caught, and excs is the list of the exceptions that need to be raised. This list contains the unhandled part of orig, if any, as well as the exceptions that were raised from the except* clauses (so they have a different traceback from orig) and those that were reraised (and have the same traceback as orig). Return the
that needs to be reraised in the end, or None if there is nothing to reraise.
Added in version 3.12.
Unicode Exception Objects
The following functions are used to create and modify Unicode exceptions from C.
*PyUnicodeDecodeError_Create(constchar*encoding, constchar*object,
length,
start,
end, constchar*reason)
Return value: New reference. Part of the
.Create a
object with the attributes encoding, object, length, start, end and reason. encoding and reason are UTF-8 encoded strings.
*PyUnicodeDecodeError_GetEncoding(
*exc)
*PyUnicodeEncodeError_GetEncoding(
*exc)
Return value: New reference. Part of the
.Return the encoding attribute of the given exception object.
*PyUnicodeDecodeError_GetObject(
*exc)
*PyUnicodeEncodeError_GetObject(
*exc)
*PyUnicodeTranslateError_GetObject(
*exc)
Return value: New reference. Part of the
.Return the object attribute of the given exception object.
intPyUnicodeDecodeError_GetStart(
*exc,
*start)
intPyUnicodeEncodeError_GetStart(
*exc,
*start)
intPyUnicodeTranslateError_GetStart(
*exc,
*start)
Part of the
.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.
If the
is an empty sequence, the resulting start is 0. Otherwise, it is clipped to [0,len(object)-1].
intPyUnicodeDecodeError_SetStart(
*exc,
start)
intPyUnicodeEncodeError_SetStart(
*exc,
start)
intPyUnicodeTranslateError_SetStart(
*exc,
start)
Part of the
.Set the start attribute of the given exception object to start. Return 0 on success, -1 on failure.
Note
While passing a negative start does not raise an exception, the corresponding getters will not consider it as a relative offset.
intPyUnicodeDecodeError_GetEnd(
*exc,
*end)
intPyUnicodeEncodeError_GetEnd(
*exc,
*end)
intPyUnicodeTranslateError_GetEnd(
*exc,
*end)
Part of the
.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.
If the
is an empty sequence, the resulting end is 0. Otherwise, it is clipped to [1,len(object)].
intPyUnicodeDecodeError_SetEnd(
*exc,
end)
intPyUnicodeEncodeError_SetEnd(
*exc,
end)
intPyUnicodeTranslateError_SetEnd(
*exc,
end)
Part of the
.Set the end attribute of the given exception object to end. Return 0 on success, -1 on failure.
*PyUnicodeDecodeError_GetReason(
*exc)
*PyUnicodeEncodeError_GetReason(
*exc)
*PyUnicodeTranslateError_GetReason(
*exc)
Return value: New reference. Part of the
.Return the reason attribute of the given exception object.
intPyUnicodeDecodeError_SetReason(
*exc, constchar*reason)
intPyUnicodeEncodeError_SetReason(
*exc, constchar*reason)
intPyUnicodeTranslateError_SetReason(
*exc, constchar*reason)
Part of the
.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). They are also not needed for tp_call implementations because the
takes care of recursion handling.
intPy_EnterRecursiveCall(constchar*where)
Part of the
since version 3.9.Marks a point where a recursive C-level call is about to be performed.
The function then checks if the stack limit is reached. If this is the case, a
is set and a nonzero value is returned. Otherwise, zero is returned.
where should be a UTF-8 encoded string such as "ininstancecheck" to be concatenated to the
message caused by the recursion depth limit.
Changed in version 3.9: This function is now also available in the
.
voidPy_LeaveRecursiveCall(void)
Part of the
since version 3.9.Ends a
. Must be called once for each successful invocation of Py_EnterRecursiveCall().
Changed in version 3.9: This function is now also available in the
.
Properly implementing
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
.
intPy_ReprEnter(
*object)
Part of the
.Called at the beginning of the
implementation to detect cycles.
If the object has already been processed, the function returns a positive integer. In that case the
implementation should return a string object indicating a cycle. As examples,
objects return {...} and
objects return [...].
The function will return a negative integer if the recursion limit is reached. In that case the
implementation should typically return NULL.
Otherwise, the function returns zero and the
implementation can continue normally.
voidPy_ReprLeave(
*object)
Part of the
.Ends a
. Must be called once for each invocation of Py_ReprEnter() that returns zero.
intPy_GetRecursionLimit(void)
Part of the
.Get the recursion limit for the current interpreter. It can be set with
. The recursion limit prevents the Python interpreter stack from growing infinitely.
This function cannot fail, and the caller must hold an
.
voidPy_SetRecursionLimit(intnew_limit)
Part of the
.Set the recursion limit for the current interpreter.
This function cannot fail, and the caller must hold an
.
Exception and warning types
All standard Python exceptions and warning categories are available as global variables whose names are PyExc_ followed by the Python exception name. These have the type
*; they are all class objects.
For completeness, here are all the variables:
Exception types
C name
Python name
*PyExc_BaseException
Part of the
.
*PyExc_BaseExceptionGroup
Part of the
since version 3.11.
*PyExc_Exception
Part of the
.
*PyExc_ArithmeticError
Part of the
.
*PyExc_AssertionError
Part of the
.
*PyExc_AttributeError
Part of the
.
*PyExc_BlockingIOError
Part of the
since version 3.7.
*PyExc_BrokenPipeError
Part of the
since version 3.7.
*PyExc_BufferError
Part of the
.
*PyExc_ChildProcessError
Part of the
since version 3.7.
*PyExc_ConnectionAbortedError
Part of the
since version 3.7.
*PyExc_ConnectionError
Part of the
since version 3.7.
*PyExc_ConnectionRefusedError
Part of the
since version 3.7.
*PyExc_ConnectionResetError
Part of the
since version 3.7.
*PyExc_EOFError
Part of the
.
*PyExc_FileExistsError
Part of the
since version 3.7.
*PyExc_FileNotFoundError
Part of the
since version 3.7.
*PyExc_FloatingPointError
Part of the
.
*PyExc_GeneratorExit
Part of the
.
*PyExc_ImportCycleError
*PyExc_ImportError
Part of the
.
*PyExc_IndentationError
Part of the
.
*PyExc_IndexError
Part of the
.
*PyExc_InterruptedError
Part of the
since version 3.7.
*PyExc_IsADirectoryError
Part of the
since version 3.7.
*PyExc_KeyError
Part of the
.
*PyExc_KeyboardInterrupt
Part of the
.
*PyExc_LookupError
Part of the
.
*PyExc_MemoryError
Part of the
.
*PyExc_ModuleNotFoundError
Part of the
since version 3.6.
*PyExc_NameError
Part of the
.
*PyExc_NotADirectoryError
Part of the
since version 3.7.
*PyExc_NotImplementedError
Part of the
.
*PyExc_OSError
Part of the
.
*PyExc_OverflowError
Part of the
.
*PyExc_PermissionError
Part of the
since version 3.7.
*PyExc_ProcessLookupError
Part of the
since version 3.7.
*PyExc_PythonFinalizationError
*PyExc_RecursionError
Part of the
since version 3.7.
*PyExc_ReferenceError
Part of the
.
*PyExc_RuntimeError
Part of the
.
*PyExc_StopAsyncIteration
Part of the
since version 3.7.
*PyExc_StopIteration
Part of the
.
*PyExc_SyntaxError
Part of the
.
*PyExc_SystemError
Part of the
.
*PyExc_SystemExit
Part of the
.
*PyExc_TabError
Part of the
.
*PyExc_TimeoutError
Part of the
since version 3.7.
*PyExc_TypeError
Part of the
.
*PyExc_UnboundLocalError
Part of the
.
*PyExc_UnicodeDecodeError
Part of the
.
*PyExc_UnicodeEncodeError
Part of the
.
*PyExc_UnicodeError
Part of the
.
*PyExc_UnicodeTranslateError
Part of the
.
*PyExc_ValueError
Part of the
.
*PyExc_ZeroDivisionError
Part of the
.
Added in version 3.3:
,
,
,
,
,
,
,
,
,
,
,
,
,
and
were introduced following
.
Added in version 3.5:
and
.
Added in version 3.6:
.
Added in version 3.11:
.
OSError aliases
The following are a compatibility aliases to
.
Changed in version 3.3: These aliases used to be separate exception types.
C name
Python name
Notes
*PyExc_EnvironmentError
Part of the
.
*PyExc_IOError
Part of the
.
*PyExc_WindowsError
Part of the
on Windows since version 3.7.
Notes:
[
]
PyExc_WindowsError is only defined on Windows; protect code that uses this by testing that the preprocessor macro MS_WINDOWS is defined.
Warning types
C name
Python name
*PyExc_Warning
Part of the
.
*PyExc_BytesWarning
Part of the
.
*PyExc_DeprecationWarning
Part of the
.
*PyExc_EncodingWarning
Part of the
since version 3.10.
*PyExc_FutureWarning
Part of the
.
*PyExc_ImportWarning
Part of the
.
*PyExc_PendingDeprecationWarning
Part of the
.
*PyExc_ResourceWarning
Part of the
since version 3.7.
*PyExc_RuntimeWarning
Part of the
.
*PyExc_SyntaxWarning
Part of the
.
*PyExc_UnicodeWarning
Part of the
.
*PyExc_UserWarning
Part of the
.
Added in version 3.2:
.
Added in version 3.10:
.
Tracebacks
PyTraceBack_Type
Part of the
.Type object for traceback objects. This is available as
in the Python layer.
intPyTraceBack_Check(
*op)
Return true if op is a traceback object, false otherwise. This function does not account for subtypes.
intPyTraceBack_Here(
*f)
Part of the
.Replace the
attribute on the current exception with a new traceback prepending f to the existing chain.
Calling this function without an exception set is undefined behavior.
This function returns 0 on success, and returns -1 with an exception set on failure.
intPyTraceBack_Print(
*tb,
*f)
Part of the
.Write the traceback tb into the file f.
This function returns 0 on success, and returns -1 with an exception set on failure.
constchar*PyUnstable_DumpTraceback(intfd,
*tstate)
This is
. It may change without warning in minor releases.
Write a trace of the Python stack in tstate into the file fd. The format looks like:
Traceback(mostrecentcallfirst):File"xxx",linexxxin<xxx>File"xxx",linexxxin<xxx>...File"xxx",linexxxin<xxx>This function is meant to debug situations such as segfaults, fatal errors, and similar. The file and function names it outputs are encoded to ASCII with backslashreplace and truncated to 500 characters. It writes only the first 100 frames; further frames are truncated with the line ....
This function will return NULL on success, or an error message on error.
This function is intended for use in crash scenarios such as signal handlers for SIGSEGV, where the interpreter may be in an inconsistent state. Given that it reads interpreter data structures that may be partially modified, the function might produce incomplete output or it may even crash itself.
The caller does not need to hold an
, nor does tstate need to be attached.
Added in version 3.15.
constchar*PyUnstable_DumpTracebackThreads(intfd,
*interp,
*current_tstate,
max_threads)
This is
. It may change without warning in minor releases.
Write the traces of all Python threads in interp into the file fd.
If interp is NULL then this function will try to identify the current interpreter using thread-specific storage. If it cannot, it will return an error.
If current_tstate is not NULL then it will be used to identify what the current thread is in the written output. If it is NULL then this function will identify the current thread using thread-specific storage. It is not an error if the function is unable to get the current Python thread state.
This function will return NULL on success, or an error message on error.
This function is meant to debug situations such as segfaults, fatal errors, and similar. It calls
for each thread. It only writes the tracebacks of the first max_threads threads, further output is truncated with the line .... If max_threads is 0, the function will use a default value of 100 for the argument.
This function is intended for use in crash scenarios such as signal handlers for SIGSEGV, where the interpreter may be in an inconsistent state. Given that it reads interpreter data structures that may be partially modified, the function might produce incomplete output or it may even crash itself.
The caller does not need to hold an
, nor does current_tstate need to be attached.
Warning
On the
, this function is not thread-safe. If another thread deletes its
while this function is being called, the process will likely crash.
Added in version 3.15.