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54 lines
6.2 KiB
HTML
54 lines
6.2 KiB
HTML
<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /><link rel="stylesheet" type="text/css" href="libvirt.css" /><link rel="SHORTCUT ICON" href="/32favicon.png" /><title>Binding for Python</title></head><body><div id="container"><div id="intro"><div id="adjustments"></div><div id="pageHeader"></div><div id="content2"><h1 class="style1">Binding for Python</h1><p>Libvirt comes with direct support for the Python language (just make sure
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you installed the libvirt-python package if not compiling from sources). Also
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note that Daniel Berrange provides <a href="http://search.cpan.org/~danberr/Sys-Virt-0.1.0/">bindings for Perl</a>
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too.</p><p>The Python binding should be complete and are mostly automatically
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generated from the formal description of the API in xml. The bindings are
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articulated around 2 classes <code>virConnect</code> and virDomain mapping to
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the C types. Functions in the C API taking either type as argument then
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becomes methods for the classes, their name is just stripped from the
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virConnect or virDomain(Get) prefix and the first letter gets converted to
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lower case, for example the C functions:</p><p><code>int <a href="html/libvirt-libvirt.html#virConnectNumOfDomains">virConnectNumOfDomains</a>
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(virConnectPtr conn);</code></p><p><code>int <a href="html/libvirt-libvirt.html#virDomainSetMaxMemory">virDomainSetMaxMemory</a>
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(virDomainPtr domain, unsigned long memory);</code></p><p>become</p><p><code>virConn::numOfDomains(self)</code></p><p><code>virDomain::setMaxMemory(self, memory)</code></p><p>This process is fully automated, you can get a summary of the conversion
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in the file libvirtclass.txt present in the python dir or in the docs.There
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is a couple of function who don't map directly to their C counterparts due to
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specificities in their argument conversions:</p><ul><li><code><a href="html/libvirt-libvirt.html#virConnectListDomains">virConnectListDomains</a></code>
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is replaced by <code>virDomain::listDomainsID(self)</code> which returns
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a list of the integer ID for the currently running domains</li>
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<li><code><a href="html/libvirt-libvirt.html#virDomainGetInfo">virDomainGetInfo</a></code>
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is replaced by <code>virDomain::info()</code> which returns a list of
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<ol><li>state: one of the state values (virDomainState)</li>
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<li>maxMemory: the maximum memory used by the domain</li>
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<li>memory: the current amount of memory used by the domain</li>
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<li>nbVirtCPU: the number of virtual CPU</li>
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<li>cpuTime: the time used by the domain in nanoseconds</li>
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</ol></li>
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</ul><p>So let's look at a simple example inspired from the <code>basic.py</code>
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test found in <code>python/tests/</code> in the source tree:</p><pre>import <span style="color: #0071FF; background-color: #FFFFFF">libvirt</span>
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import sys
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conn = <span style="color: #0071FF; background-color: #FFFFFF">libvirt</span>.openReadOnly(None)
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if conn == None:
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print 'Failed to open connection to the hypervisor'
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sys.exit(1)
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try:
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dom0 = conn.<span style="color: #007F00; background-color: #FFFFFF">lookupByName</span>("Domain-0")
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except:
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print 'Failed to find the main domain'
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sys.exit(1)
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print "Domain 0: id %d running %s" % (dom0.<span style="color: #FF0080; background-color: #FFFFFF">ID</span>(), dom0.<span style="color: #FF0080; background-color: #FFFFFF">OSType</span>())
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print dom0.<span style="color: #FF0080; background-color: #FFFFFF">info</span>()</pre><p>There is not much to comment about it, it really is a straight mapping
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from the C API, the only points to notice are:</p><ul><li>the import of the module called <code><span style="color: #0071FF; background-color: #FFFFFF">libvirt</span></code></li>
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<li>getting a connection to the hypervisor, in that case using the
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openReadOnly function allows the code to execute as a normal user.</li>
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<li>getting an object representing the Domain 0 using <span style="color: #007F00; background-color: #FFFFFF">lookupByName</span></li>
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<li>if the domain is not found a libvirtError exception will be raised</li>
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<li>extracting and printing some informations about the domain using
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various <span style="color: #E50073; background-color: #FFFFFF">methods</span>
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associated to the virDomain class.</li>
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</ul></div></div><div class="linkList2"><div class="llinks2"><h3 class="links2"><span>main menu</span></h3><ul><li><a href="index.html">Home</a></li><li><a href="news.html">Releases</a></li><li><a href="intro.html">Introduction</a></li><li><a href="architecture.html">libvirt architecture</a></li><li><a href="downloads.html">Downloads</a></li><li><a href="format.html">XML Format</a></li><li><a href="python.html">Binding for Python</a></li><li><a href="errors.html">Handling of errors</a></li><li><a href="FAQ.html">FAQ</a></li><li><a href="bugs.html">Reporting bugs and getting help</a></li><li><a href="html/index.html">API Menu</a></li><li><a href="examples/index.html">C code examples</a></li><li><a href="ChangeLog.html">Recent Changes</a></li></ul></div><div class="llinks2"><h3 class="links2"><span>related links</span></h3><ul><li><a href="https://www.redhat.com/archives/libvir-list/">Mail archive</a></li><li><a href="https://bugzilla.redhat.com/bugzilla/buglist.cgi?product=Fedora+Core&component=libvirt&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED&bug_status=MODIFIED&short_desc_type=allwordssubstr&short_desc=&long_desc_type=allwordssubstr">Open bugs</a></li><li><a href="http://search.cpan.org/~danberr/Sys-Virt-0.1.0/">Perl bindings</a></li><li><a href="http://www.cl.cam.ac.uk/Research/SRG/netos/xen/index.html">Xen project</a></li><li><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="12" value="Search..." /><input name="submit" type="submit" value="Go" /></form></li><li><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-90x34.gif" alt="Made with Libxml2 Logo" /></a></li></ul><p class="credits">Graphics and design by <a href="mail:dfong@redhat.com">Diana Fong</a></p></div></div><div id="bottom"><p class="p1"></p></div></div></body></html>
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