python lxml: case insensitive xpath tag name matching

Question

I'm using python + lxml to parse a spss file.

There seems to be many threads on this topic but the answers don't particular help me.

The answers I have come across:

- lower-case the entire input before parsing; 
- if you know the complete list of tags in advance

For me these suggestion would take too much time.

Instead I would like to match strings only when necessary.

Here is the line of code I would like to edit:

xpath("//definition//variable[@name='"+tag_name+"']")

How can I get a hit if tag_name is:

tag_name = "Q1top"
tag_name = "q1Top"
tag_name = "q1TOP"
etc

I'm guessing some form of regex would be in order???

Answer 1

Alternatively, you can incorporate regex from http://exslt.org/regular-expressions namespace in the XPath, for example :

ns = {"re": "http://exslt.org/regular-expressions"}
query = "//definition//variable[re:test(@name, '^{0}$', 'i')]".format(tag_name)
result = tree.xpath(query, namespaces=ns)

Answer 2

Using local-name, translate XPath functions:

>>> import lxml.etree
>>> 
>>> root = lxml.etree.fromstring('''
... <root>
...     <parent>
...         <Q1top>1</Q1top>
...         <q1Top>2</q1Top>
...         <q1TOP>3</q1TOP>
...     </parent>
... </root>
... ''')
>>> root.xpath('.//*[translate(local-name(), '
...            '"ABCDEFGHIJKLMNOPQRSTUVWXYZ", '
...            '"abcdefghijklmnopqrstuvwxyz")="q1top"]')
[<Element Q1top at 0x7fd663354a28>,
 <Element q1Top at 0x7fd663354830>,
 <Element q1TOP at 0x7fd6633549e0>]

UPDATE

>>> root.xpath('.//*[translate(local-name(), '
...            '"QTOP", '
...            '"qtop")="q1top"]')
[<Element Q1top at 0x7fd663354a28>,
 <Element q1Top at 0x7fd663354830>,
 <Element q1TOP at 0x7fd6633549e0>]