What is the name for "for $x in ... return ..." syntax in XPath?

Question

I have this xpath:

/document/offers/offer/concat(price/text(), for $r in . return 'default-value'[not($r/price/text())])

which solves my problem (default value for missing tags) for this document:

<document>
  <company>
    <ceo>Elon Musk</ceo>
    <employees>13058</employees>
    <address>
      <city>Palo Alto</city>
      <state>California</state>
      <country>USA</country>
    </address>
  </company>
  <offers>
    <offer avail="0">
      <id>1</id>
      <model>Tesla Roadster</model>
      <imageUrl>https://www.teslamotors.com/sites/default/files/styles/blog-picture_2x_1400xvar_/public/0H8E6227_1.jpg</imageUrl>
    </offer>
    <offer avail="1">
      <id>2</id>
      <model>Tesla Model S</model>
      <price>63400.00</price>
      <offerUrl>https://www.teslamotors.com/models</offerUrl>
      <imageUrl>https://www.teslamotors.com/tesla_theme/assets/img/models/section-initial.jpg</imageUrl>
    </offer>
    <offer avail="1">
      <id>3</id>
      <model>Tesla Model X</model>
      <price>69300.00</price>
      <offerUrl>https://www.teslamotors.com/modelx</offerUrl>
      <imageUrl>https://www.teslamotors.com/tesla_theme/assets/img/modelx/section-exterior-profile.jpg</imageUrl>
    </offer>
    <offer avail="1">
      <id>4</id>
      <model>Tesla Model 3</model>
      <price>35000.00</price>
      <offerUrl>https://www.teslamotors.com/model3</offerUrl>
      <imageUrl>https://www.teslamotors.com/sites/default/files/images/model-3/gallery/gallery-1.jpg</imageUrl>
    </offer>
  </offers>
</document>

by returning:

default-value
63400.00
69300.00
35000.00

According to http://videlibri.sourceforge.net/cgi-bin/xidelcgi, this works but I cannot make this work with lxml in python. Right now I don't know even how to google equivalent of this type of xpath. So... how those "inner fors" are called in xpaths?

Answer 1

That is an xpath2 for-expressions which is not supported by lxml or xml.etree in python. You could replicate it using a for loop

from lxml import  etree

xml = etree.parse("the_file")
for node in xml.xpath("//document/offers/offer"):
    pr = node.xpath("./price")
    print(pr[0].text if pr else "Default-value")

Which would give you:

Default-value
63400.00
69300.00
35000.00