Build a regular expression to find id in an href

<?xml version="1.0" encoding="utf-8"?>
<?dctm xml_app="elearningContent"?>
<!DOCTYPE OnlineContent PUBLIC "-//ISDOFSD//DTD Online Content//EN" "file:C:/dmExport/New%20Folder%20(2)/ISDOFSDdev/elearningContent/OnlineContent.dtd">
<OnlineContent outputclass="Graphic Down" id="OnlineContent_955627C91D8743B98DCB8BD9BE379DE8">
    <title>Text and Popup</title>
    <OnlineContentBody>
    	<lcInstruction id="lcInstruction_770F26218C064A84BFA1813562173970">
    		<p>This is an example of a plain text screen with an attached popup.</p>
    		<p>
    			Popups are used to display additional content in a popup window. A <xref scope="local" type="topic" format="dita" href="dctm://ISDOFSDdev/37004e1f800021f3?DMS_OBJECT_SPEC=RELATION_ID">link is provided</xref> in the main text of the screen, which may clicked on to open a popup. A screen may contain <xref scope="local" type="topic" format="dita" href="dctm://ISDOFSDdev/37004e1f800021f4?DMS_OBJECT_SPEC=RELATION_ID">more than one popup</xref>.
    		</p>
    	</lcInstruction>
    </OnlineContentBody>
    <OnlinePopup id="OnlinePopup_AFE53E2CACBF4D8196E6360D4DDB6B70">
    	<title>A Popup</title>
    	<OnlinePopupBody>
    		<p>This is an example of popup content.</p>
    		<p>A popup may contain one or more paragraphs of text. They may also contain lists, like this:</p>
    		<ul id="ul_7812991BBBDD4995B7499A9557C4EA9C">
    			<li id="li_E83BDB28EC494B98BFF3DD5924AF855E">An item in a list</li>
    			<li id="li_270F2A3A85BA4E6EBF98CB4023344475">Another item in a list</li>
    		</ul>
    		<p>A numbered list is demonstrated in the second popup.</p>
    	</OnlinePopupBody>
    </OnlinePopup>
    <OnlinePopup id="OnlinePopup_5AE081BFB97043CE99F39A9E4A063332">
    	<title>Another Popup</title>
    	<OnlinePopupBody>
    		<p>This is the second popup on this screen, containing a numbered list.</p>
    		<ol id="ol_EF18C080E7CC40B7998DEB75772367A6">
    			<li id="li_91B42F1B886B4CF887C001577C14B3F0">An item in a list</li>
    			<li id="li_95C4F32E093843FAB985A3F6981A7D07">Another item in a list</li>
    		</ol>
    	</OnlinePopupBody>
    </OnlinePopup>
</OnlineContent>

[a-fA-F0-9]+(?=?DMS_OBJECT_SPEC=RELATION_ID)

<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    	>
    	<xsl:output method="text" indent="no"/>
    	<xsl:template match="*[@href]">
    		<xsl:if test="contains(@href, 'RELATION_ID')">
    			<xsl:value-of select="@href"/>
			<xsl:text>&#xa;</xsl:text>
    		</xsl:if>
    		<xsl:apply-templates select="*"/>
    	</xsl:template>
    	<xsl:template match="*">
    		<xsl:apply-templates select="*"/>
    	</xsl:template>
</xsl:stylesheet>

C:Documents and SettingsferEscritorio>msxsl.exe -xw example.xml example-xslt.xsl > out.txt

<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:fn="http://www.w3.org/2005/xpath-functions" >
    	<xsl:output method="text" indent="no"/>
    	<xsl:template match="*[@href]">
    		<xsl:if test="fn:contains(@href, 'RELATION_ID')">
    			<xsl:value-of select="fn:replace(@href,'.*/([^/]*)?.*', '$1')"/>
    			<xsl:text>&#xa;</xsl:text>
    		</xsl:if>
    		<xsl:apply-templates select="*"/>
    	</xsl:template>
    	<xsl:template match="*">
    		<xsl:apply-templates select="*"/>
    	</xsl:template>
</xsl:stylesheet>

C:Documents and SettingsferEscritorio>AltovaXML -xslt2 example-xslt.xsl -in example.xml

expr = re.compile('href=.*?/(.*?)?.*?=RELATION_ID', re.MULTILINE)

for x in expr.finditer(test_string): # iterate through all matches
   s = x.group(1) # get the one and only group of the match
   ss = s.split("/") # split off the ISDOFSDdev
   s = ss[len(ss) - 1] # grab the last element
   print s # print it

37004e1f800021f3
37004e1f800021f4