[New-bugs-announce] [issue42104] xml.etree should support contains() function

Tue Oct 20 22:54:16 EDT 2020

New submission from karl <karl+pythonbugs at la-grange.net>:

In XPath 1.0 
The function contains() is available 

> Function: boolean contains(string, string)
> The contains function returns true if the first argument string contains the second argument string, and otherwise returns false.

In https://www.w3.org/TR/1999/REC-xpath-19991116/#function-contains

```
<body>
   <p class="doc">One attribute: doc</p>
   <p class="doc test">Two Attributes: doc test</p>
   <p class="test">One Attribute: test</p>
</body>
```

Currently, we can do this

```
>>> from lxml import etree
>>> root = etree.fromstring("""<body>
...    <p class="doc">One attribute</p>
...    <p class="doc test">Two Attributes: doc test</p>
...    <p class="doc2 test">Two Attributes: doc2 test</p>
... </body>
... """)
>>> elts = root.xpath("//p[@class='doc']")
>>> elts, etree.tostring(elts[0])
([<Element p at 0x102670900>], b'<p class="doc">One attribute</p>\n   ')
```

One way of extracting the list of 2 elements which contains the attribute doc with XPath is:

```
>>> root.xpath("//p[contains(@class, 'doc')]")
[<Element p at 0x1026708c0>, <Element p at 0x102670780>]
>>> [etree.tostring(elt) for elt in root.xpath("//p[contains(@class, 'doc')]")]
[b'<p class="doc">One attribute: doc</p>\n   ', b'<p class="doc test">Two Attributes: doc test</p>\n   ']
```

There is no easy way to extract all elements containing a "doc" value in a multi-values attribute in python 3.10 with xml.etree, which is quite common in html. 

```
>>> import xml.etree.ElementTree as ET
>>> root = ET.fromstring("""<body>
...    <p class="doc">One attribute: doc</p>
...    <p class="doc test">Two Attributes: doc test</p>
...    <p class="test">One Attribute: test</p>
... </body>"""
... )
>>> root.xpath("//p[contains(@class, 'doc')]")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'xml.etree.ElementTree.Element' object has no attribute 'xpath'
```

----------
components: Library (Lib)
messages: 379185
nosy: karlcow
priority: normal
severity: normal
status: open
title: xml.etree should support contains() function
type: enhancement
versions: Python 3.10

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue42104>
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