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 <section id="module-exceptions">
<h1>6. Built-in Exceptions<a class="headerlink" href="#module-exceptions" title="Permalink to this headline">¶</a></h1>
Exceptions should be class objects. The exceptions are defined in the module
<a class="reference internal" href="#module-exceptions" title="exceptions: Standard exception classes."><code class="xref py py-mod docutils literal notranslate">exceptions</code></a>. This module never needs to be imported explicitly: the
exceptions are provided in the built-in namespace as well as the
<a class="reference internal" href="#module-exceptions" title="exceptions: Standard exception classes."><code class="xref py py-mod docutils literal notranslate">exceptions</code></a> module.
For class exceptions, in a <a class="reference internal" href="../reference/compound_stmts.html#try"><code class="xref std std-keyword docutils literal notranslate">try</code></a> statement with an <a class="reference internal" href="../reference/compound_stmts.html#except"><code class="xref std std-keyword docutils literal notranslate">except</code></a>
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.
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
<a class="reference internal" href="../reference/simple_stmts.html#raise"><code class="xref std std-keyword docutils literal notranslate">raise</code></a> statement. If the exception class is derived from the standard
root class <a class="reference internal" href="#exceptions.BaseException" title="exceptions.BaseException"><code class="xref py py-exc docutils literal notranslate">BaseException</code></a>, the associated value is present as the
exception instance’s <code class="xref py py-attr docutils literal notranslate">args</code> 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 <a class="reference internal" href="#exceptions.Exception" title="exceptions.Exception"><code class="xref py py-exc docutils literal notranslate">Exception</code></a>
class or one of its subclasses, and not from <a class="reference internal" href="#exceptions.BaseException" title="exceptions.BaseException"><code class="xref py py-exc docutils literal notranslate">BaseException</code></a>. More
information on defining exceptions is available in the Python Tutorial under
<a class="reference internal" href="../tutorial/errors.html#tut-userexceptions">User-defined Exceptions</a>.
The following exceptions are only used as base classes for other exceptions.
<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.BaseException">
exception exceptions.BaseException<a class="headerlink" href="#exceptions.BaseException" title="Permalink to this definition">¶</a></dt>
<dd>The base class for all built-in exceptions. It is not meant to be directly
inherited by user-defined classes (for that, use <a class="reference internal" href="#exceptions.Exception" title="exceptions.Exception"><code class="xref py py-exc docutils literal notranslate">Exception</code></a>). If
<a class="reference internal" href="functions.html#str" title="str"><code class="xref py py-func docutils literal notranslate">str()</code></a> or <a class="reference internal" href="functions.html#unicode" title="unicode"><code class="xref py py-func docutils literal notranslate">unicode()</code></a> 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.
<div class="versionadded">
New in version 2.5.
</div>
<dl class="py attribute">
<dt class="sig sig-object py" id="exceptions.BaseException.args">
args<a class="headerlink" href="#exceptions.BaseException.args" title="Permalink to this definition">¶</a></dt>
<dd>The tuple of arguments given to the exception constructor. Some built-in
exceptions (like <a class="reference internal" href="#exceptions.IOError" title="exceptions.IOError"><code class="xref py py-exc docutils literal notranslate">IOError</code></a>) 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.
</dd></dl>

</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.Exception">
exception exceptions.Exception<a class="headerlink" href="#exceptions.Exception" title="Permalink to this definition">¶</a></dt>
<dd>All built-in, non-system-exiting exceptions are derived from this class. All
user-defined exceptions should also be derived from this class.
<div class="versionchanged">
Changed in version 2.5: Changed to inherit from <a class="reference internal" href="#exceptions.BaseException" title="exceptions.BaseException"><code class="xref py py-exc docutils literal notranslate">BaseException</code></a>.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.StandardError">
exception exceptions.StandardError<a class="headerlink" href="#exceptions.StandardError" title="Permalink to this definition">¶</a></dt>
<dd>The base class for all built-in exceptions except <a class="reference internal" href="#exceptions.StopIteration" title="exceptions.StopIteration"><code class="xref py py-exc docutils literal notranslate">StopIteration</code></a>,
<a class="reference internal" href="#exceptions.GeneratorExit" title="exceptions.GeneratorExit"><code class="xref py py-exc docutils literal notranslate">GeneratorExit</code></a>, <a class="reference internal" href="#exceptions.KeyboardInterrupt" title="exceptions.KeyboardInterrupt"><code class="xref py py-exc docutils literal notranslate">KeyboardInterrupt</code></a> and <a class="reference internal" href="#exceptions.SystemExit" title="exceptions.SystemExit"><code class="xref py py-exc docutils literal notranslate">SystemExit</code></a>.
<a class="reference internal" href="#exceptions.StandardError" title="exceptions.StandardError"><code class="xref py py-exc docutils literal notranslate">StandardError</code></a> itself is derived from <a class="reference internal" href="#exceptions.Exception" title="exceptions.Exception"><code class="xref py py-exc docutils literal notranslate">Exception</code></a>.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.ArithmeticError">
exception exceptions.ArithmeticError<a class="headerlink" href="#exceptions.ArithmeticError" title="Permalink to this definition">¶</a></dt>
<dd>The base class for those built-in exceptions that are raised for various
arithmetic errors: <a class="reference internal" href="#exceptions.OverflowError" title="exceptions.OverflowError"><code class="xref py py-exc docutils literal notranslate">OverflowError</code></a>, <a class="reference internal" href="#exceptions.ZeroDivisionError" title="exceptions.ZeroDivisionError"><code class="xref py py-exc docutils literal notranslate">ZeroDivisionError</code></a>,
<a class="reference internal" href="#exceptions.FloatingPointError" title="exceptions.FloatingPointError"><code class="xref py py-exc docutils literal notranslate">FloatingPointError</code></a>.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.BufferError">
exception exceptions.BufferError<a class="headerlink" href="#exceptions.BufferError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when a <a class="reference internal" href="../c-api/buffer.html#bufferobjects">buffer</a> related operation cannot be
performed.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.LookupError">
exception exceptions.LookupError<a class="headerlink" href="#exceptions.LookupError" title="Permalink to this definition">¶</a></dt>
<dd>The base class for the exceptions that are raised when a key or index used on
a mapping or sequence is invalid: <a class="reference internal" href="#exceptions.IndexError" title="exceptions.IndexError"><code class="xref py py-exc docutils literal notranslate">IndexError</code></a>, <a class="reference internal" href="#exceptions.KeyError" title="exceptions.KeyError"><code class="xref py py-exc docutils literal notranslate">KeyError</code></a>. This
can be raised directly by <a class="reference internal" href="codecs.html#codecs.lookup" title="codecs.lookup"><code class="xref py py-func docutils literal notranslate">codecs.lookup()</code></a>.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.EnvironmentError">
exception exceptions.EnvironmentError<a class="headerlink" href="#exceptions.EnvironmentError" title="Permalink to this definition">¶</a></dt>
<dd>The base class for exceptions that can occur outside the Python system:
<a class="reference internal" href="#exceptions.IOError" title="exceptions.IOError"><code class="xref py py-exc docutils literal notranslate">IOError</code></a>, <a class="reference internal" href="#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal notranslate">OSError</code></a>. When exceptions of this type are created with a
2-tuple, the first item is available on the instance’s <a class="reference internal" href="errno.html#module-errno" title="errno: Standard errno system symbols."><code class="xref py py-attr docutils literal notranslate">errno</code></a> attribute
(it is assumed to be an error number), and the second item is available on the
<code class="xref py py-attr docutils literal notranslate">strerror</code> attribute (it is usually the associated error message). The
tuple itself is also available on the <code class="xref py py-attr docutils literal notranslate">args</code> attribute.
<div class="versionadded">
New in version 1.5.2.
</div>
When an <a class="reference internal" href="#exceptions.EnvironmentError" title="exceptions.EnvironmentError"><code class="xref py py-exc docutils literal notranslate">EnvironmentError</code></a> exception is instantiated with a 3-tuple, the
first two items are available as above, while the third item is available on the
<code class="xref py py-attr docutils literal notranslate">filename</code> attribute. However, for backwards compatibility, the
<code class="xref py py-attr docutils literal notranslate">args</code> attribute contains only a 2-tuple of the first two constructor
arguments.
The <code class="xref py py-attr docutils literal notranslate">filename</code> attribute is <code class="docutils literal notranslate">None</code> when this exception is created with
other than 3 arguments. The <a class="reference internal" href="errno.html#module-errno" title="errno: Standard errno system symbols."><code class="xref py py-attr docutils literal notranslate">errno</code></a> and <code class="xref py py-attr docutils literal notranslate">strerror</code> attributes are
also <code class="docutils literal notranslate">None</code> when the instance was created with other than 2 or 3 arguments.
In this last case, <code class="xref py py-attr docutils literal notranslate">args</code> contains the verbatim constructor arguments as a
tuple.
</dd></dl>

The following exceptions are the exceptions that are actually raised.
<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.AssertionError">
exception exceptions.AssertionError<a class="headerlink" href="#exceptions.AssertionError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when an <a class="reference internal" href="../reference/simple_stmts.html#assert"><code class="xref std std-keyword docutils literal notranslate">assert</code></a> statement fails.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.AttributeError">
exception exceptions.AttributeError<a class="headerlink" href="#exceptions.AttributeError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when an attribute reference (see <a class="reference internal" href="../reference/expressions.html#attribute-references">Attribute references</a>) or
assignment fails. (When an object does not support attribute references or
attribute assignments at all, <a class="reference internal" href="#exceptions.TypeError" title="exceptions.TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> is raised.)
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.EOFError">
exception exceptions.EOFError<a class="headerlink" href="#exceptions.EOFError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when one of the built-in functions (<a class="reference internal" href="functions.html#input" title="input"><code class="xref py py-func docutils literal notranslate">input()</code></a> or <a class="reference internal" href="functions.html#raw_input" title="raw_input"><code class="xref py py-func docutils literal notranslate">raw_input()</code></a>)
hits an end-of-file condition (EOF) without reading any data. (N.B.: the
<a class="reference internal" href="stdtypes.html#file.read" title="file.read"><code class="xref py py-meth docutils literal notranslate">file.read()</code></a> and <a class="reference internal" href="stdtypes.html#file.readline" title="file.readline"><code class="xref py py-meth docutils literal notranslate">file.readline()</code></a> methods return an empty string
when they hit EOF.)
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.FloatingPointError">
exception exceptions.FloatingPointError<a class="headerlink" href="#exceptions.FloatingPointError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when a floating point operation fails. This exception is always defined,
but can only be raised when Python is configured with the
<code class="docutils literal notranslate">--with-fpectl</code> option, or the <code class="xref py py-const docutils literal notranslate">WANT_SIGFPE_HANDLER</code> symbol is
defined in the <code class="file docutils literal notranslate">pyconfig.h</code> file.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.GeneratorExit">
exception exceptions.GeneratorExit<a class="headerlink" href="#exceptions.GeneratorExit" title="Permalink to this definition">¶</a></dt>
<dd>Raised when a <a class="reference internal" href="../glossary.html#term-generator">generator</a>'s <code class="xref py py-meth docutils literal notranslate">close()</code> method is called. It
directly inherits from <a class="reference internal" href="#exceptions.BaseException" title="exceptions.BaseException"><code class="xref py py-exc docutils literal notranslate">BaseException</code></a> instead of <a class="reference internal" href="#exceptions.StandardError" title="exceptions.StandardError"><code class="xref py py-exc docutils literal notranslate">StandardError</code></a>
since it is technically not an error.
<div class="versionadded">
New in version 2.5.
</div>
<div class="versionchanged">
Changed in version 2.6: Changed to inherit from <a class="reference internal" href="#exceptions.BaseException" title="exceptions.BaseException"><code class="xref py py-exc docutils literal notranslate">BaseException</code></a>.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.IOError">
exception exceptions.IOError<a class="headerlink" href="#exceptions.IOError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when an I/O operation (such as a <a class="reference internal" href="../reference/simple_stmts.html#print"><code class="xref std std-keyword docutils literal notranslate">print</code></a> statement, the built-in
<a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> 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 <a class="reference internal" href="#exceptions.EnvironmentError" title="exceptions.EnvironmentError"><code class="xref py py-exc docutils literal notranslate">EnvironmentError</code></a>. See the discussion above
for more information on exception instance attributes.
<div class="versionchanged">
Changed in version 2.6: Changed <a class="reference internal" href="socket.html#socket.error" title="socket.error"><code class="xref py py-exc docutils literal notranslate">socket.error</code></a> to use this as a base class.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.ImportError">
exception exceptions.ImportError<a class="headerlink" href="#exceptions.ImportError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when an <a class="reference internal" href="../reference/simple_stmts.html#import"><code class="xref std std-keyword docutils literal notranslate">import</code></a> statement fails to find the module definition
or when a <code class="docutils literal notranslate">from ... import</code> fails to find a name that is to be imported.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.IndexError">
exception exceptions.IndexError<a class="headerlink" href="#exceptions.IndexError" title="Permalink to this definition">¶</a></dt>
<dd>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,
<a class="reference internal" href="#exceptions.TypeError" title="exceptions.TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> is raised.)
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.KeyError">
exception exceptions.KeyError<a class="headerlink" href="#exceptions.KeyError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when a mapping (dictionary) key is not found in the set of existing keys.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.KeyboardInterrupt">
exception exceptions.KeyboardInterrupt<a class="headerlink" href="#exceptions.KeyboardInterrupt" title="Permalink to this definition">¶</a></dt>
<dd>Raised when the user hits the interrupt key (normally <kbd class="kbd compound docutils literal notranslate"><kbd class="kbd docutils literal notranslate">Control</kbd>-<kbd class="kbd docutils literal notranslate">C</kbd></kbd> or
<kbd class="kbd docutils literal notranslate">Delete</kbd>). During execution, a check for interrupts is made regularly.
Interrupts typed when a built-in function <a class="reference internal" href="functions.html#input" title="input"><code class="xref py py-func docutils literal notranslate">input()</code></a> or <a class="reference internal" href="functions.html#raw_input" title="raw_input"><code class="xref py py-func docutils literal notranslate">raw_input()</code></a> is
waiting for input also raise this exception. The exception inherits from
<a class="reference internal" href="#exceptions.BaseException" title="exceptions.BaseException"><code class="xref py py-exc docutils literal notranslate">BaseException</code></a> so as to not be accidentally caught by code that catches
<a class="reference internal" href="#exceptions.Exception" title="exceptions.Exception"><code class="xref py py-exc docutils literal notranslate">Exception</code></a> and thus prevent the interpreter from exiting.
<div class="versionchanged">
Changed in version 2.5: Changed to inherit from <a class="reference internal" href="#exceptions.BaseException" title="exceptions.BaseException"><code class="xref py py-exc docutils literal notranslate">BaseException</code></a>.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.MemoryError">
exception exceptions.MemoryError<a class="headerlink" href="#exceptions.MemoryError" title="Permalink to this definition">¶</a></dt>
<dd>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 <code class="xref c c-func docutils literal notranslate">malloc()</code> 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.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.NameError">
exception exceptions.NameError<a class="headerlink" href="#exceptions.NameError" title="Permalink to this definition">¶</a></dt>
<dd>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.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.NotImplementedError">
exception exceptions.NotImplementedError<a class="headerlink" href="#exceptions.NotImplementedError" title="Permalink to this definition">¶</a></dt>
<dd>This exception is derived from <a class="reference internal" href="#exceptions.RuntimeError" title="exceptions.RuntimeError"><code class="xref py py-exc docutils literal notranslate">RuntimeError</code></a>. In user defined base
classes, abstract methods should raise this exception when they require derived
classes to override the method.
<div class="versionadded">
New in version 1.5.2.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.OSError">
exception exceptions.OSError<a class="headerlink" href="#exceptions.OSError" title="Permalink to this definition">¶</a></dt>
<dd>This exception is derived from <a class="reference internal" href="#exceptions.EnvironmentError" title="exceptions.EnvironmentError"><code class="xref py py-exc docutils literal notranslate">EnvironmentError</code></a>. It is raised when a
function returns a system-related error (not for illegal argument types or
other incidental errors). The <a class="reference internal" href="errno.html#module-errno" title="errno: Standard errno system symbols."><code class="xref py py-attr docutils literal notranslate">errno</code></a> attribute is a numeric error
code from <code class="xref c c-data docutils literal notranslate">errno</code>, and the <code class="xref py py-attr docutils literal notranslate">strerror</code> attribute is the
corresponding string, as would be printed by the C function <code class="xref c c-func docutils literal notranslate">perror()</code>.
See the module <a class="reference internal" href="errno.html#module-errno" title="errno: Standard errno system symbols."><code class="xref py py-mod docutils literal notranslate">errno</code></a>, which contains names for the error codes defined
by the underlying operating system.
For exceptions that involve a file system path (such as <code class="xref py py-func docutils literal notranslate">chdir()</code> or
<code class="xref py py-func docutils literal notranslate">unlink()</code>), the exception instance will contain a third attribute,
<code class="xref py py-attr docutils literal notranslate">filename</code>, which is the file name passed to the function.
<div class="versionadded">
New in version 1.5.2.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.OverflowError">
exception exceptions.OverflowError<a class="headerlink" href="#exceptions.OverflowError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when the result of an arithmetic operation is too large to be
represented. This cannot occur for long integers (which would rather raise
<a class="reference internal" href="#exceptions.MemoryError" title="exceptions.MemoryError"><code class="xref py py-exc docutils literal notranslate">MemoryError</code></a> 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.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.ReferenceError">
exception exceptions.ReferenceError<a class="headerlink" href="#exceptions.ReferenceError" title="Permalink to this definition">¶</a></dt>
<dd>This exception is raised when a weak reference proxy, created by the
<a class="reference internal" href="weakref.html#weakref.proxy" title="weakref.proxy"><code class="xref py py-func docutils literal notranslate">weakref.proxy()</code></a> function, is used to access an attribute of the referent
after it has been garbage collected. For more information on weak references,
see the <a class="reference internal" href="weakref.html#module-weakref" title="weakref: Support for weak references and weak dictionaries."><code class="xref py py-mod docutils literal notranslate">weakref</code></a> module.
<div class="versionadded">
New in version 2.2: Previously known as the <a class="reference internal" href="weakref.html#weakref.ReferenceError" title="weakref.ReferenceError"><code class="xref py py-exc docutils literal notranslate">weakref.ReferenceError</code></a> exception.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.RuntimeError">
exception exceptions.RuntimeError<a class="headerlink" href="#exceptions.RuntimeError" title="Permalink to this definition">¶</a></dt>
<dd>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.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.StopIteration">
exception exceptions.StopIteration<a class="headerlink" href="#exceptions.StopIteration" title="Permalink to this definition">¶</a></dt>
<dd>Raised by an <a class="reference internal" href="../glossary.html#term-iterator">iterator</a>'s <a class="reference internal" href="stdtypes.html#iterator.next" title="iterator.next"><code class="xref py py-meth docutils literal notranslate">next()</code></a> method to signal that
there are no further values. This is derived from <a class="reference internal" href="#exceptions.Exception" title="exceptions.Exception"><code class="xref py py-exc docutils literal notranslate">Exception</code></a> rather
than <a class="reference internal" href="#exceptions.StandardError" title="exceptions.StandardError"><code class="xref py py-exc docutils literal notranslate">StandardError</code></a>, since this is not considered an error in its
normal application.
<div class="versionadded">
New in version 2.2.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.SyntaxError">
exception exceptions.SyntaxError<a class="headerlink" href="#exceptions.SyntaxError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when the parser encounters a syntax error. This may occur in an
<a class="reference internal" href="../reference/simple_stmts.html#import"><code class="xref std std-keyword docutils literal notranslate">import</code></a> statement, in an <a class="reference internal" href="../reference/simple_stmts.html#exec"><code class="xref std std-keyword docutils literal notranslate">exec</code></a> statement, in a call to the
built-in function <a class="reference internal" href="functions.html#eval" title="eval"><code class="xref py py-func docutils literal notranslate">eval()</code></a> or <a class="reference internal" href="functions.html#input" title="input"><code class="xref py py-func docutils literal notranslate">input()</code></a>, or when reading the initial
script or standard input (also interactively).
Instances of this class have attributes <code class="xref py py-attr docutils literal notranslate">filename</code>, <code class="xref py py-attr docutils literal notranslate">lineno</code>,
<code class="xref py py-attr docutils literal notranslate">offset</code> and <code class="xref py py-attr docutils literal notranslate">text</code> for easier access to the details. <a class="reference internal" href="functions.html#str" title="str"><code class="xref py py-func docutils literal notranslate">str()</code></a>
of the exception instance returns only the message.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.IndentationError">
exception exceptions.IndentationError<a class="headerlink" href="#exceptions.IndentationError" title="Permalink to this definition">¶</a></dt>
<dd>Base class for syntax errors related to incorrect indentation. This is a
subclass of <a class="reference internal" href="#exceptions.SyntaxError" title="exceptions.SyntaxError"><code class="xref py py-exc docutils literal notranslate">SyntaxError</code></a>.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.TabError">
exception exceptions.TabError<a class="headerlink" href="#exceptions.TabError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when indentation contains an inconsistent use of tabs and spaces.
This is a subclass of <a class="reference internal" href="#exceptions.IndentationError" title="exceptions.IndentationError"><code class="xref py py-exc docutils literal notranslate">IndentationError</code></a>.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.SystemError">
exception exceptions.SystemError<a class="headerlink" href="#exceptions.SystemError" title="Permalink to this definition">¶</a></dt>
<dd>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 (<code class="docutils literal notranslate">sys.version</code>; 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.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.SystemExit">
exception exceptions.SystemExit<a class="headerlink" href="#exceptions.SystemExit" title="Permalink to this definition">¶</a></dt>
<dd>This exception is raised by the <a class="reference internal" href="sys.html#sys.exit" title="sys.exit"><code class="xref py py-func docutils literal notranslate">sys.exit()</code></a> 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 <code class="xref c c-func docutils literal notranslate">exit()</code> function); if it is <code class="docutils literal notranslate">None</code>, 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 <code class="xref py py-attr docutils literal notranslate">code</code> which is set to the proposed exit
status or error message (defaulting to <code class="docutils literal notranslate">None</code>). Also, this exception derives
directly from <a class="reference internal" href="#exceptions.BaseException" title="exceptions.BaseException"><code class="xref py py-exc docutils literal notranslate">BaseException</code></a> and not <a class="reference internal" href="#exceptions.StandardError" title="exceptions.StandardError"><code class="xref py py-exc docutils literal notranslate">StandardError</code></a>, since it is not
technically an error.
A call to <a class="reference internal" href="sys.html#sys.exit" title="sys.exit"><code class="xref py py-func docutils literal notranslate">sys.exit()</code></a> is translated into an exception so that clean-up
handlers (<a class="reference internal" href="../reference/compound_stmts.html#finally"><code class="xref std std-keyword docutils literal notranslate">finally</code></a> clauses of <a class="reference internal" href="../reference/compound_stmts.html#try"><code class="xref std std-keyword docutils literal notranslate">try</code></a> statements) can be
executed, and so that a debugger can execute a script without running the risk
of losing control. The <a class="reference internal" href="os.html#os._exit" title="os._exit"><code class="xref py py-func docutils literal notranslate">os._exit()</code></a> function can be used if it is
absolutely positively necessary to exit immediately (for example, in the child
process after a call to <a class="reference internal" href="os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate">os.fork()</code></a>).
The exception inherits from <a class="reference internal" href="#exceptions.BaseException" title="exceptions.BaseException"><code class="xref py py-exc docutils literal notranslate">BaseException</code></a> instead of <a class="reference internal" href="#exceptions.StandardError" title="exceptions.StandardError"><code class="xref py py-exc docutils literal notranslate">StandardError</code></a>
or <a class="reference internal" href="#exceptions.Exception" title="exceptions.Exception"><code class="xref py py-exc docutils literal notranslate">Exception</code></a> so that it is not accidentally caught by code that catches
<a class="reference internal" href="#exceptions.Exception" title="exceptions.Exception"><code class="xref py py-exc docutils literal notranslate">Exception</code></a>. This allows the exception to properly propagate up and cause
the interpreter to exit.
<div class="versionchanged">
Changed in version 2.5: Changed to inherit from <a class="reference internal" href="#exceptions.BaseException" title="exceptions.BaseException"><code class="xref py py-exc docutils literal notranslate">BaseException</code></a>.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.TypeError">
exception exceptions.TypeError<a class="headerlink" href="#exceptions.TypeError" title="Permalink to this definition">¶</a></dt>
<dd>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.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.UnboundLocalError">
exception exceptions.UnboundLocalError<a class="headerlink" href="#exceptions.UnboundLocalError" title="Permalink to this definition">¶</a></dt>
<dd>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
<a class="reference internal" href="#exceptions.NameError" title="exceptions.NameError"><code class="xref py py-exc docutils literal notranslate">NameError</code></a>.
<div class="versionadded">
New in version 2.0.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.UnicodeError">
exception exceptions.UnicodeError<a class="headerlink" href="#exceptions.UnicodeError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when a Unicode-related encoding or decoding error occurs. It is a
subclass of <a class="reference internal" href="#exceptions.ValueError" title="exceptions.ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a>.
<a class="reference internal" href="#exceptions.UnicodeError" title="exceptions.UnicodeError"><code class="xref py py-exc docutils literal notranslate">UnicodeError</code></a> has attributes that describe the encoding or decoding
error. For example, <code class="docutils literal notranslate">err.object[err.start:err.end]</code> gives the particular
invalid input that the codec failed on.
<dl class="py attribute">
<dt class="sig sig-object py" id="exceptions.UnicodeError.encoding">
encoding<a class="headerlink" href="#exceptions.UnicodeError.encoding" title="Permalink to this definition">¶</a></dt>
<dd>The name of the encoding that raised the error.
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="exceptions.UnicodeError.reason">
reason<a class="headerlink" href="#exceptions.UnicodeError.reason" title="Permalink to this definition">¶</a></dt>
<dd>A string describing the specific codec error.
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="exceptions.UnicodeError.object">
object<a class="headerlink" href="#exceptions.UnicodeError.object" title="Permalink to this definition">¶</a></dt>
<dd>The object the codec was attempting to encode or decode.
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="exceptions.UnicodeError.start">
start<a class="headerlink" href="#exceptions.UnicodeError.start" title="Permalink to this definition">¶</a></dt>
<dd>The first index of invalid data in <a class="reference internal" href="functions.html#object" title="object"><code class="xref py py-attr docutils literal notranslate">object</code></a>.
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="exceptions.UnicodeError.end">
end<a class="headerlink" href="#exceptions.UnicodeError.end" title="Permalink to this definition">¶</a></dt>
<dd>The index after the last invalid data in <a class="reference internal" href="functions.html#object" title="object"><code class="xref py py-attr docutils literal notranslate">object</code></a>.
</dd></dl>

<div class="versionadded">
New in version 2.0.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.UnicodeEncodeError">
exception exceptions.UnicodeEncodeError<a class="headerlink" href="#exceptions.UnicodeEncodeError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when a Unicode-related error occurs during encoding. It is a subclass of
<a class="reference internal" href="#exceptions.UnicodeError" title="exceptions.UnicodeError"><code class="xref py py-exc docutils literal notranslate">UnicodeError</code></a>.
<div class="versionadded">
New in version 2.3.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.UnicodeDecodeError">
exception exceptions.UnicodeDecodeError<a class="headerlink" href="#exceptions.UnicodeDecodeError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when a Unicode-related error occurs during decoding. It is a subclass of
<a class="reference internal" href="#exceptions.UnicodeError" title="exceptions.UnicodeError"><code class="xref py py-exc docutils literal notranslate">UnicodeError</code></a>.
<div class="versionadded">
New in version 2.3.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.UnicodeTranslateError">
exception exceptions.UnicodeTranslateError<a class="headerlink" href="#exceptions.UnicodeTranslateError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when a Unicode-related error occurs during translating. It is a subclass
of <a class="reference internal" href="#exceptions.UnicodeError" title="exceptions.UnicodeError"><code class="xref py py-exc docutils literal notranslate">UnicodeError</code></a>.
<div class="versionadded">
New in version 2.3.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.ValueError">
exception exceptions.ValueError<a class="headerlink" href="#exceptions.ValueError" title="Permalink to this definition">¶</a></dt>
<dd>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 <a class="reference internal" href="#exceptions.IndexError" title="exceptions.IndexError"><code class="xref py py-exc docutils literal notranslate">IndexError</code></a>.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.VMSError">
exception exceptions.VMSError<a class="headerlink" href="#exceptions.VMSError" title="Permalink to this definition">¶</a></dt>
<dd>Only available on VMS. Raised when a VMS-specific error occurs.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.WindowsError">
exception exceptions.WindowsError<a class="headerlink" href="#exceptions.WindowsError" title="Permalink to this definition">¶</a></dt>
<dd>Raised when a Windows-specific error occurs or when the error number does not
correspond to an <code class="xref c c-data docutils literal notranslate">errno</code> value. The <code class="xref py py-attr docutils literal notranslate">winerror</code> and
<code class="xref py py-attr docutils literal notranslate">strerror</code> values are created from the return values of the
<code class="xref c c-func docutils literal notranslate">GetLastError()</code> and <code class="xref c c-func docutils literal notranslate">FormatMessage()</code> functions from the Windows
Platform API. The <a class="reference internal" href="errno.html#module-errno" title="errno: Standard errno system symbols."><code class="xref py py-attr docutils literal notranslate">errno</code></a> value maps the <code class="xref py py-attr docutils literal notranslate">winerror</code> value to
corresponding <code class="docutils literal notranslate">errno.h</code> values. This is a subclass of <a class="reference internal" href="#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal notranslate">OSError</code></a>.
<div class="versionadded">
New in version 2.0.
</div>
<div class="versionchanged">
Changed in version 2.5: Previous versions put the <code class="xref c c-func docutils literal notranslate">GetLastError()</code> codes into <a class="reference internal" href="errno.html#module-errno" title="errno: Standard errno system symbols."><code class="xref py py-attr docutils literal notranslate">errno</code></a>.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.ZeroDivisionError">
exception exceptions.ZeroDivisionError<a class="headerlink" href="#exceptions.ZeroDivisionError" title="Permalink to this definition">¶</a></dt>
<dd>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.
</dd></dl>

The following exceptions are used as warning categories; see the <a class="reference internal" href="warnings.html#module-warnings" title="warnings: Issue warning messages and control their disposition."><code class="xref py py-mod docutils literal notranslate">warnings</code></a>
module for more information.
<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.Warning">
exception exceptions.Warning<a class="headerlink" href="#exceptions.Warning" title="Permalink to this definition">¶</a></dt>
<dd>Base class for warning categories.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.UserWarning">
exception exceptions.UserWarning<a class="headerlink" href="#exceptions.UserWarning" title="Permalink to this definition">¶</a></dt>
<dd>Base class for warnings generated by user code.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.DeprecationWarning">
exception exceptions.DeprecationWarning<a class="headerlink" href="#exceptions.DeprecationWarning" title="Permalink to this definition">¶</a></dt>
<dd>Base class for warnings about deprecated features.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.PendingDeprecationWarning">
exception exceptions.PendingDeprecationWarning<a class="headerlink" href="#exceptions.PendingDeprecationWarning" title="Permalink to this definition">¶</a></dt>
<dd>Base class for warnings about features which will be deprecated in the future.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.SyntaxWarning">
exception exceptions.SyntaxWarning<a class="headerlink" href="#exceptions.SyntaxWarning" title="Permalink to this definition">¶</a></dt>
<dd>Base class for warnings about dubious syntax.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.RuntimeWarning">
exception exceptions.RuntimeWarning<a class="headerlink" href="#exceptions.RuntimeWarning" title="Permalink to this definition">¶</a></dt>
<dd>Base class for warnings about dubious runtime behavior.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.FutureWarning">
exception exceptions.FutureWarning<a class="headerlink" href="#exceptions.FutureWarning" title="Permalink to this definition">¶</a></dt>
<dd>Base class for warnings about constructs that will change semantically in the
future.
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.ImportWarning">
exception exceptions.ImportWarning<a class="headerlink" href="#exceptions.ImportWarning" title="Permalink to this definition">¶</a></dt>
<dd>Base class for warnings about probable mistakes in module imports.
<div class="versionadded">
New in version 2.5.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.UnicodeWarning">
exception exceptions.UnicodeWarning<a class="headerlink" href="#exceptions.UnicodeWarning" title="Permalink to this definition">¶</a></dt>
<dd>Base class for warnings related to Unicode.
<div class="versionadded">
New in version 2.5.
</div>
</dd></dl>

<dl class="py exception">
<dt class="sig sig-object py" id="exceptions.BytesWarning">
exception exceptions.BytesWarning<a class="headerlink" href="#exceptions.BytesWarning" title="Permalink to this definition">¶</a></dt>
<dd>Base class for warnings related to bytes and bytearray.
<div class="versionadded">
New in version 2.6.
</div>
</dd></dl>

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