Example for setting (multiple) parameters in Python LXML XSLT

Question

Looked for the solution to this problem for a while since the documentation isn't really clear on it.

I ended up using the method below, and thought I'd share back.

Answer 1

Apparently you can chain parameter arguments when applying the XSLT to the original xml tree. I found the most reliable way is to always use the tree.XSLT.strparam() method for wrapping the argument values. Not really needed I guess for simpler types like string or integers. But this method works regardless.

<xsl:stylesheet version="1.0"
   xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <xsl:output method="xml" omit-xml-declaration="no"/>
   <xsl:param name="var1"/>
   <xsl:param name="var2"/>
   <!-- actual sheet omitted because example -->
</xsl:stylesheet>

from lxml import etree

var = "variable string"

original_tree = etree.parse("original.xml")
xslt_tree = etree.parse("transform.xsl")
xslt = etree.XSLT(xslt_tree)
lom_tree = xslt(original_tree, var1=etree.XSLT.strparam("str_example"), var2=etree.XSLT.strparam(var))

print(etree.tostring(lom_tree, pretty_print=True))

Answer 2

Actually the concern about using strparam is only that when you don't read carefully enough the xlst documentation of lxml, you don't realize that anything you pass as just a string is interpreted as a xpath !

  transform = etree.XSLT(xslt_tree)
  doc_root = etree.XML('<a><b>Text</b></a>')

  ### "5" is a numeric value, so it's sent as is
  result = transform(doc_root, a="5")

  ### "/a/b/text()" *and* "test" are both interpreted as a xpath !
  result = transform(doc_root, a="/a/b/text()")
  result = transform(doc_root, a="test")

  ### to actually send the string "test", you *must* quote it twice or use strparam
  result = transform(doc_root, a="'test'")
  result = transform(doc_root, a=etree.XSLT.strparam("test")