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abc.rst.txt	7219	0644	editdlrm
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aetools.rst.txt	3532	0644	editdlrm
aetypes.rst.txt	4257	0644	editdlrm
aifc.rst.txt	7086	0644	editdlrm
al.rst.txt	5309	0644	editdlrm
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anydbm.rst.txt	4111	0644	editdlrm
archiving.rst.txt	424	0644	editdlrm
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ast.rst.txt	10111	0644	editdlrm
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atexit.rst.txt	3910	0644	editdlrm
audioop.rst.txt	10395	0644	editdlrm
autogil.rst.txt	1015	0644	editdlrm
base64.rst.txt	6252	0644	editdlrm
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bastion.rst.txt	2611	0644	editdlrm
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calendar.rst.txt	11282	0644	editdlrm
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crypt.rst.txt	2292	0644	editdlrm
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csv.rst.txt	22757	0644	editdlrm
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easydialogs.rst.txt	10346	0644	editdlrm
email-examples.rst.txt	1271	0644	editdlrm
email.charset.rst.txt	9654	0644	editdlrm
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fpectl.rst.txt	4171	0644	editdlrm
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fractions.rst.txt	5297	0644	editdlrm
framework.rst.txt	11444	0644	editdlrm
frameworks.rst.txt	378	0644	editdlrm
ftplib.rst.txt	15720	0644	editdlrm
functions.rst.txt	75554	0644	editdlrm
functools.rst.txt	7448	0644	editdlrm
future_builtins.rst.txt	2010	0644	editdlrm
gc.rst.txt	9014	0644	editdlrm
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gensuitemodule.rst.txt	3113	0644	editdlrm
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gettext.rst.txt	29040	0644	editdlrm
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hotshot.rst.txt	4289	0644	editdlrm
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imp.rst.txt	12593	0644	editdlrm
importlib.rst.txt	1126	0644	editdlrm
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index.rst.txt	2287	0644	editdlrm
inspect.rst.txt	28151	0644	editdlrm
internet.rst.txt	950	0644	editdlrm
intro.rst.txt	2803	0644	editdlrm
io.rst.txt	39015	0644	editdlrm
ipc.rst.txt	630	0644	editdlrm
itertools.rst.txt	36324	0644	editdlrm
jpeg.rst.txt	3858	0644	editdlrm
json.rst.txt	25545	0644	editdlrm
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logging.handlers.rst.txt	28153	0644	editdlrm
logging.rst.txt	46882	0644	editdlrm
mac.rst.txt	791	0644	editdlrm
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macostools.rst.txt	4017	0644	editdlrm
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mailbox.rst.txt	68129	0644	editdlrm
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markup.rst.txt	1249	0644	editdlrm
marshal.rst.txt	5689	0644	editdlrm
math.rst.txt	10920	0644	editdlrm
md5.rst.txt	2815	0644	editdlrm
mhlib.rst.txt	3966	0644	editdlrm
mimetools.rst.txt	4504	0644	editdlrm
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mimewriter.rst.txt	3360	0644	editdlrm
mimify.rst.txt	3519	0644	editdlrm
miniaeframe.rst.txt	2564	0644	editdlrm
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mmap.rst.txt	10481	0644	editdlrm
modulefinder.rst.txt	3380	0644	editdlrm
modules.rst.txt	382	0644	editdlrm
msilib.rst.txt	19062	0644	editdlrm
msvcrt.rst.txt	4346	0644	editdlrm
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mutex.rst.txt	1939	0644	editdlrm
netdata.rst.txt	432	0644	editdlrm
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new.rst.txt	2653	0644	editdlrm
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optparse.rst.txt	77101	0644	editdlrm
os.path.rst.txt	13094	0644	editdlrm
os.rst.txt	82580	0644	editdlrm
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parser.rst.txt	15385	0644	editdlrm
pdb.rst.txt	16043	0644	editdlrm
persistence.rst.txt	826	0644	editdlrm
pickle.rst.txt	37262	0644	editdlrm
pickletools.rst.txt	1997	0644	editdlrm
pipes.rst.txt	3786	0644	editdlrm
pkgutil.rst.txt	7714	0644	editdlrm
platform.rst.txt	9554	0644	editdlrm
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popen2.rst.txt	7022	0644	editdlrm
poplib.rst.txt	6220	0644	editdlrm
posix.rst.txt	3630	0644	editdlrm
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pprint.rst.txt	9071	0644	editdlrm
profile.rst.txt	28666	0644	editdlrm
pty.rst.txt	1762	0644	editdlrm
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pyclbr.rst.txt	3296	0644	editdlrm
pydoc.rst.txt	4083	0644	editdlrm
pyexpat.rst.txt	28891	0644	editdlrm
python.rst.txt	514	0644	editdlrm
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queue.rst.txt	7034	0644	editdlrm
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readline.rst.txt	10513	0644	editdlrm
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restricted.rst.txt	3327	0644	editdlrm
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rfc822.rst.txt	14037	0644	editdlrm
rlcompleter.rst.txt	2494	0644	editdlrm
robotparser.rst.txt	2190	0644	editdlrm
runpy.rst.txt	6938	0644	editdlrm
sched.rst.txt	4644	0644	editdlrm
scrolledtext.rst.txt	1379	0644	editdlrm
select.rst.txt	20705	0644	editdlrm
sets.rst.txt	14973	0644	editdlrm
sgi.rst.txt	322	0644	editdlrm
sgmllib.rst.txt	10664	0644	editdlrm
sha.rst.txt	2807	0644	editdlrm
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signal.rst.txt	10719	0644	editdlrm
simplehttpserver.rst.txt	4559	0644	editdlrm
simplexmlrpcserver.rst.txt	10881	0644	editdlrm
site.rst.txt	7880	0644	editdlrm
smtpd.rst.txt	2464	0644	editdlrm
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sndhdr.rst.txt	1759	0644	editdlrm
socket.rst.txt	40765	0644	editdlrm
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sqlite3.rst.txt	35448	0644	editdlrm
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string.rst.txt	44085	0644	editdlrm
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__main__.rst.txt	535	0644	editdlrm

.. _bltin-exceptions: Built-in Exceptions =================== .. module:: exceptions :synopsis: Standard exception classes. Exceptions should be class objects. The exceptions are defined in the module :mod:`exceptions`. This module never needs to be imported explicitly: the exceptions are provided in the built-in namespace as well as the :mod:`exceptions` module. .. index:: statement: try statement: except For class exceptions, in a :keyword:`try` statement with an :keyword:`except` clause that mentions a particular class, that clause also handles any exception classes derived from that class (but not exception classes from which *it* is derived). Two exception classes that are not related via subclassing are never equivalent, even if they have the same name. .. index:: statement: raise The built-in exceptions listed below can be generated by the interpreter or built-in functions. Except where mentioned, they have an "associated value" indicating the detailed cause of the error. This may be a string or a tuple containing several items of information (e.g., an error code and a string explaining the code). The associated value is the second argument to the :keyword:`raise` statement. If the exception class is derived from the standard root class :exc:`BaseException`, the associated value is present as the exception instance's :attr:`args` attribute. User code can raise built-in exceptions. This can be used to test an exception handler or to report an error condition "just like" the situation in which the interpreter raises the same exception; but beware that there is nothing to prevent user code from raising an inappropriate error. The built-in exception classes can be subclassed to define new exceptions; programmers are encouraged to derive new exceptions from the :exc:`Exception` class or one of its subclasses, and not from :exc:`BaseException`. More information on defining exceptions is available in the Python Tutorial under :ref:`tut-userexceptions`. The following exceptions are only used as base classes for other exceptions. .. exception:: BaseException The base class for all built-in exceptions. It is not meant to be directly inherited by user-defined classes (for that, use :exc:`Exception`). If :func:`str` or :func:`unicode` is called on an instance of this class, the representation of the argument(s) to the instance are returned, or the empty string when there were no arguments. .. versionadded:: 2.5 .. attribute:: args The tuple of arguments given to the exception constructor. Some built-in exceptions (like :exc:`IOError`) expect a certain number of arguments and assign a special meaning to the elements of this tuple, while others are usually called only with a single string giving an error message. .. exception:: Exception All built-in, non-system-exiting exceptions are derived from this class. All user-defined exceptions should also be derived from this class. .. versionchanged:: 2.5 Changed to inherit from :exc:`BaseException`. .. exception:: StandardError The base class for all built-in exceptions except :exc:`StopIteration`, :exc:`GeneratorExit`, :exc:`KeyboardInterrupt` and :exc:`SystemExit`. :exc:`StandardError` itself is derived from :exc:`Exception`. .. exception:: ArithmeticError The base class for those built-in exceptions that are raised for various arithmetic errors: :exc:`OverflowError`, :exc:`ZeroDivisionError`, :exc:`FloatingPointError`. .. exception:: BufferError Raised when a :ref:`buffer ` related operation cannot be performed. .. exception:: LookupError The base class for the exceptions that are raised when a key or index used on a mapping or sequence is invalid: :exc:`IndexError`, :exc:`KeyError`. This can be raised directly by :func:`codecs.lookup`. .. exception:: EnvironmentError The base class for exceptions that can occur outside the Python system: :exc:`IOError`, :exc:`OSError`. When exceptions of this type are created with a 2-tuple, the first item is available on the instance's :attr:`errno` attribute (it is assumed to be an error number), and the second item is available on the :attr:`strerror` attribute (it is usually the associated error message). The tuple itself is also available on the :attr:`args` attribute. .. versionadded:: 1.5.2 When an :exc:`EnvironmentError` exception is instantiated with a 3-tuple, the first two items are available as above, while the third item is available on the :attr:`filename` attribute. However, for backwards compatibility, the :attr:`args` attribute contains only a 2-tuple of the first two constructor arguments. The :attr:`filename` attribute is ``None`` when this exception is created with other than 3 arguments. The :attr:`errno` and :attr:`strerror` attributes are also ``None`` when the instance was created with other than 2 or 3 arguments. In this last case, :attr:`args` contains the verbatim constructor arguments as a tuple. The following exceptions are the exceptions that are actually raised. .. exception:: AssertionError .. index:: statement: assert Raised when an :keyword:`assert` statement fails. .. exception:: AttributeError Raised when an attribute reference (see :ref:`attribute-references`) or assignment fails. (When an object does not support attribute references or attribute assignments at all, :exc:`TypeError` is raised.) .. exception:: EOFError Raised when one of the built-in functions (:func:`input` or :func:`raw_input`) hits an end-of-file condition (EOF) without reading any data. (N.B.: the :meth:`file.read` and :meth:`file.readline` methods return an empty string when they hit EOF.) .. exception:: FloatingPointError Raised when a floating point operation fails. This exception is always defined, but can only be raised when Python is configured with the ``--with-fpectl`` option, or the :const:`WANT_SIGFPE_HANDLER` symbol is defined in the :file:`pyconfig.h` file. .. exception:: GeneratorExit Raised when a :term:`generator`\'s :meth:`close` method is called. It directly inherits from :exc:`BaseException` instead of :exc:`StandardError` since it is technically not an error. .. versionadded:: 2.5 .. versionchanged:: 2.6 Changed to inherit from :exc:`BaseException`. .. exception:: IOError Raised when an I/O operation (such as a :keyword:`print` statement, the built-in :func:`open` function or a method of a file object) fails for an I/O-related reason, e.g., "file not found" or "disk full". This class is derived from :exc:`EnvironmentError`. See the discussion above for more information on exception instance attributes. .. versionchanged:: 2.6 Changed :exc:`socket.error` to use this as a base class. .. exception:: ImportError Raised when an :keyword:`import` statement fails to find the module definition or when a ``from ... import`` fails to find a name that is to be imported. .. exception:: IndexError Raised when a sequence subscript is out of range. (Slice indices are silently truncated to fall in the allowed range; if an index is not a plain integer, :exc:`TypeError` is raised.) .. XXX xref to sequences .. exception:: KeyError Raised when a mapping (dictionary) key is not found in the set of existing keys. .. XXX xref to mapping objects? .. exception:: KeyboardInterrupt Raised when the user hits the interrupt key (normally :kbd:`Control-C` or :kbd:`Delete`). During execution, a check for interrupts is made regularly. Interrupts typed when a built-in function :func:`input` or :func:`raw_input` is waiting for input also raise this exception. The exception inherits from :exc:`BaseException` so as to not be accidentally caught by code that catches :exc:`Exception` and thus prevent the interpreter from exiting. .. versionchanged:: 2.5 Changed to inherit from :exc:`BaseException`. .. exception:: MemoryError Raised when an operation runs out of memory but the situation may still be rescued (by deleting some objects). The associated value is a string indicating what kind of (internal) operation ran out of memory. Note that because of the underlying memory management architecture (C's :c:func:`malloc` function), the interpreter may not always be able to completely recover from this situation; it nevertheless raises an exception so that a stack traceback can be printed, in case a run-away program was the cause. .. exception:: NameError Raised when a local or global name is not found. This applies only to unqualified names. The associated value is an error message that includes the name that could not be found. .. exception:: NotImplementedError This exception is derived from :exc:`RuntimeError`. In user defined base classes, abstract methods should raise this exception when they require derived classes to override the method. .. versionadded:: 1.5.2 .. exception:: OSError .. index:: module: errno This exception is derived from :exc:`EnvironmentError`. It is raised when a function returns a system-related error (not for illegal argument types or other incidental errors). The :attr:`errno` attribute is a numeric error code from :c:data:`errno`, and the :attr:`strerror` attribute is the corresponding string, as would be printed by the C function :c:func:`perror`. See the module :mod:`errno`, which contains names for the error codes defined by the underlying operating system. For exceptions that involve a file system path (such as :func:`chdir` or :func:`unlink`), the exception instance will contain a third attribute, :attr:`filename`, which is the file name passed to the function. .. versionadded:: 1.5.2 .. exception:: OverflowError Raised when the result of an arithmetic operation is too large to be represented. This cannot occur for long integers (which would rather raise :exc:`MemoryError` than give up) and for most operations with plain integers, which return a long integer instead. Because of the lack of standardization of floating point exception handling in C, most floating point operations also aren't checked. .. exception:: ReferenceError This exception is raised when a weak reference proxy, created by the :func:`weakref.proxy` function, is used to access an attribute of the referent after it has been garbage collected. For more information on weak references, see the :mod:`weakref` module. .. versionadded:: 2.2 Previously known as the :exc:`weakref.ReferenceError` exception. .. exception:: RuntimeError Raised when an error is detected that doesn't fall in any of the other categories. The associated value is a string indicating what precisely went wrong. .. exception:: StopIteration Raised by an :term:`iterator`\'s :meth:`~iterator.next` method to signal that there are no further values. This is derived from :exc:`Exception` rather than :exc:`StandardError`, since this is not considered an error in its normal application. .. versionadded:: 2.2 .. exception:: SyntaxError Raised when the parser encounters a syntax error. This may occur in an :keyword:`import` statement, in an :keyword:`exec` statement, in a call to the built-in function :func:`eval` or :func:`input`, or when reading the initial script or standard input (also interactively). Instances of this class have attributes :attr:`filename`, :attr:`lineno`, :attr:`offset` and :attr:`text` for easier access to the details. :func:`str` of the exception instance returns only the message. .. exception:: IndentationError Base class for syntax errors related to incorrect indentation. This is a subclass of :exc:`SyntaxError`. .. exception:: TabError Raised when indentation contains an inconsistent use of tabs and spaces. This is a subclass of :exc:`IndentationError`. .. exception:: SystemError Raised when the interpreter finds an internal error, but the situation does not look so serious to cause it to abandon all hope. The associated value is a string indicating what went wrong (in low-level terms). You should report this to the author or maintainer of your Python interpreter. Be sure to report the version of the Python interpreter (``sys.version``; it is also printed at the start of an interactive Python session), the exact error message (the exception's associated value) and if possible the source of the program that triggered the error. .. exception:: SystemExit This exception is raised by the :func:`sys.exit` function. When it is not handled, the Python interpreter exits; no stack traceback is printed. If the associated value is a plain integer, it specifies the system exit status (passed to C's :c:func:`exit` function); if it is ``None``, the exit status is zero; if it has another type (such as a string), the object's value is printed and the exit status is one. Instances have an attribute :attr:`!code` which is set to the proposed exit status or error message (defaulting to ``None``). Also, this exception derives directly from :exc:`BaseException` and not :exc:`StandardError`, since it is not technically an error. A call to :func:`sys.exit` is translated into an exception so that clean-up handlers (:keyword:`finally` clauses of :keyword:`try` statements) can be executed, and so that a debugger can execute a script without running the risk of losing control. The :func:`os._exit` function can be used if it is absolutely positively necessary to exit immediately (for example, in the child process after a call to :func:`os.fork`). The exception inherits from :exc:`BaseException` instead of :exc:`StandardError` or :exc:`Exception` so that it is not accidentally caught by code that catches :exc:`Exception`. This allows the exception to properly propagate up and cause the interpreter to exit. .. versionchanged:: 2.5 Changed to inherit from :exc:`BaseException`. .. exception:: TypeError Raised when an operation or function is applied to an object of inappropriate type. The associated value is a string giving details about the type mismatch. .. exception:: UnboundLocalError Raised when a reference is made to a local variable in a function or method, but no value has been bound to that variable. This is a subclass of :exc:`NameError`. .. versionadded:: 2.0 .. exception:: UnicodeError Raised when a Unicode-related encoding or decoding error occurs. It is a subclass of :exc:`ValueError`. :exc:`UnicodeError` has attributes that describe the encoding or decoding error. For example, ``err.object[err.start:err.end]`` gives the particular invalid input that the codec failed on. .. attribute:: encoding The name of the encoding that raised the error. .. attribute:: reason A string describing the specific codec error. .. attribute:: object The object the codec was attempting to encode or decode. .. attribute:: start The first index of invalid data in :attr:`object`. .. attribute:: end The index after the last invalid data in :attr:`object`. .. versionadded:: 2.0 .. exception:: UnicodeEncodeError Raised when a Unicode-related error occurs during encoding. It is a subclass of :exc:`UnicodeError`. .. versionadded:: 2.3 .. exception:: UnicodeDecodeError Raised when a Unicode-related error occurs during decoding. It is a subclass of :exc:`UnicodeError`. .. versionadded:: 2.3 .. exception:: UnicodeTranslateError Raised when a Unicode-related error occurs during translating. It is a subclass of :exc:`UnicodeError`. .. versionadded:: 2.3 .. exception:: ValueError Raised when an operation or function receives an argument that has the right type but an inappropriate value, and the situation is not described by a more precise exception such as :exc:`IndexError`. .. exception:: VMSError Only available on VMS. Raised when a VMS-specific error occurs. .. exception:: WindowsError Raised when a Windows-specific error occurs or when the error number does not correspond to an :c:data:`errno` value. The :attr:`winerror` and :attr:`strerror` values are created from the return values of the :c:func:`GetLastError` and :c:func:`FormatMessage` functions from the Windows Platform API. The :attr:`errno` value maps the :attr:`winerror` value to corresponding ``errno.h`` values. This is a subclass of :exc:`OSError`. .. versionadded:: 2.0 .. versionchanged:: 2.5 Previous versions put the :c:func:`GetLastError` codes into :attr:`errno`. .. exception:: ZeroDivisionError Raised when the second argument of a division or modulo operation is zero. The associated value is a string indicating the type of the operands and the operation. The following exceptions are used as warning categories; see the :mod:`warnings` module for more information. .. exception:: Warning Base class for warning categories. .. exception:: UserWarning Base class for warnings generated by user code. .. exception:: DeprecationWarning Base class for warnings about deprecated features. .. exception:: PendingDeprecationWarning Base class for warnings about features which will be deprecated in the future. .. exception:: SyntaxWarning Base class for warnings about dubious syntax. .. exception:: RuntimeWarning Base class for warnings about dubious runtime behavior. .. exception:: FutureWarning Base class for warnings about constructs that will change semantically in the future. .. exception:: ImportWarning Base class for warnings about probable mistakes in module imports. .. versionadded:: 2.5 .. exception:: UnicodeWarning Base class for warnings related to Unicode. .. versionadded:: 2.5 Exception hierarchy ------------------- The class hierarchy for built-in exceptions is: .. literalinclude:: ../../Lib/test/exception_hierarchy.txt