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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<!-- Created on September 16, 2020 by texi2html 5.0

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<head>

<title>The Python X Library: 4.2 CatchError</title>

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</head>

<td valign="middle" align="left">[<a href="python-xlib_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>

<td valign="middle" align="left">[Index]</td>

</tr></table>

<hr>

<h2 class="section">4.2 CatchError</h2>

<p><code>error.CatchError</code> is an object which can be used as an error

handler. It collects an error matching any of the specified types,

which can be retrieved later. If several errors occur, only the last

one is remembered.

</p>

<dl>

<dt><a name="index-CatchError"></a>Class: <strong>CatchError</strong><em> ( *errors )</em></dt>

<dd>

<p>Create a new error handler object. Initialize by providing all error

classes you are interested in as arguments. If no error classes are

provided at all, this means that all errors will be considered.

</p>

</dd></dl>

<p>Pass the <code>error.CatchError</code> object as the <code>onerror</code> parameter

to X object methods. If these methods generated any errors matching the

ones specified, it can be retrieved with the following functions:

</p>

<dl>

<dt><a name="index-get_005ferror-on-CatchError"></a>Method on CatchError: <strong>get_error</strong><em> ( )</em></dt>

<dd>

<p>Return the last error object caught, or None if no matching errors has

occured.

</p>

</dd></dl>

<dl>

<dt><a name="index-get_005frequest-on-CatchError"></a>Method on CatchError: <strong>get_request</strong><em> ( )</em></dt>

<dd>

<p>Return the request object for the last error caught, or None if no

matching errors has occured.

</p>

</dd></dl>

<p><code>error.CatchError</code> objects can be reused:

</p>

<dl>

<dt><a name="index-reset-on-CatchError"></a>Method on CatchError: <strong>reset</strong><em> ( )</em></dt>

<dd>

<p>Forget any caught error.

</p>

</dd></dl>

<p>Since the X protocol is mostly asynchronous any error we’re watching for

might not have been received when we call <code>get_error</code>. To make

sure that the request has been processed by the server and any error

generated has been received by the Xlib, we must synchronize with the

server.

</p>

<p>An example of using <code>error.CatchError</code>:

</p>

<pre class="example"># Resize and the foo window

# If it has been destroyed since we looked at it the last time,

# reset variable foo to None

# Create a error handler for BadWindow errors

ec = error.CatchError(error.BadWindow)

# Perform the operation

foo.configure(width = 100, height = 200, onerror = ec)

# Sync communication with server

display.sync()

# And check if there was any error

if ec.get_error():

foo = None

</pre></div>

<hr>

<td valign="middle" align="left">[<a href="python-xlib_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>

<td valign="middle" align="left">[Index]</td>

</tr></table>

<p>

This document was generated on <i>September 16, 2020</i> using <a href="http://www.nongnu.org/texi2html/"><i>texi2html 5.0</i></a>.

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