Python XSLT Logic, Loops & Sorting (for-each, if, choose)
XSLT provides rich procedural and functional flow constructs: <xsl:for-each> iterates over node sets, <xsl:sort> sorts elements before rendering, <xsl:if> provides conditional checks, and <xsl:choose>/<xsl:when>/<xsl:otherwise> enables multi-way switch branching.
"XSLT logic tags are like a spreadsheet pivot table: you can loop through every row (<xsl:for-each>), sort alphabetically (<xsl:sort>), highlight VIP accounts in red (<xsl:if>), and assign category badges (<xsl:choose>)."
Deep Dive: How It Works
<xsl:for-each select="path">: Loops through all matching elements.
<xsl:sort select="field" order="ascending|descending" />: Sorts nodes inside for-each.
<xsl:if test="boolean_xpath">: Renders content only if condition evaluates to true.
<xsl:choose>: Multi-branch container with <xsl:when test="..."> and <xsl:otherwise> fallback.
Syntax Blueprint
<xsl:for-each select="catalog/book"> <xsl:sort select="price" /> <xsl:if test="price > 30">...</xsl:if> </xsl:for-each>
Loops over books, sorts by price, and conditionally formats expensive titles.
Core Rules to Remember
Common Beginner Traps & How to Fix Them
Using raw > or < in xsl:if test expressions.Why it happens: XSLT is valid XML, so unescaped > breaks XML parser syntax.
How to fix: Always write > for > and < for < inside test attributes (e.g. test="price > 50").
Live Interactive Example
Hit Run Code to see it liveYour Turn: Micro Challenge
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Filter items with xsl:if
- Write an `<xsl:if test="stock > 0">` that outputs `<p>In Stock</p>` inside.
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