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<H2><A NAME="SECTION0052010000000000000000"> </A>
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3.20.1 Warning Categories
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<P>
There are a number of built-in exceptions that represent warning
categories. This categorization is useful to be able to filter out
groups of warnings. The following warnings category classes are
currently defined:
<P>
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<th align="left"><b>Class</b> </th>
<th align="left"><b>Description</b> </th>
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<P>
<tr><td align="left" valign="baseline"><tt class="exception">Warning</tt></td>
<td align="left">This is the base class of all warning category
classes. It is a subclass of <tt class="exception">Exception</tt>.</td><P>
<tr><td align="left" valign="baseline"><tt class="exception">UserWarning</tt></td>
<td align="left">The default category for <tt class="function">warn()</tt>.</td><P>
<tr><td align="left" valign="baseline"><tt class="exception">DeprecationWarning</tt></td>
<td align="left">Base category for warnings about
deprecated features.</td><P>
<tr><td align="left" valign="baseline"><tt class="exception">SyntaxWarning</tt></td>
<td align="left">Base category for warnings about dubious
syntactic features.</td><P>
<tr><td align="left" valign="baseline"><tt class="exception">RuntimeWarning</tt></td>
<td align="left">Base category for warnings about dubious
runtime features.</td><P>
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<P>
While these are technically built-in exceptions, they are documented
here, because conceptually they belong to the warnings mechanism.
<P>
User code can define additional warning categories by subclassing one
of the standard warning categories. A warning category must always be
a subclass of the <tt class="exception">Warning</tt> class.
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<span class="release-info">Release 2.2, documentation updated on December 21, 2001.</span>
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