genshi.path

Basic support for evaluating XPath expressions against streams.

>>> from genshi.input import XML
>>> doc = XML('''<doc>
...  <items count="4">
...       <item status="new">
...         <summary>Foo</summary>
...       </item>
...       <item status="closed">
...         <summary>Bar</summary>
...       </item>
...       <item status="closed" resolution="invalid">
...         <summary>Baz</summary>
...       </item>
...       <item status="closed" resolution="fixed">
...         <summary>Waz</summary>
...       </item>
...   </items>
... </doc>''')
>>> print(doc.select('items/item[@status="closed" and '
...     '(@resolution="invalid" or not(@resolution))]/summary/text()'))
BarBaz

Because the XPath engine operates on markup streams (as opposed to tree structures), it only implements a subset of the full XPath 1.0 language.

class genshi.path.Path(text, filename=None, lineno=-1)

Implements basic XPath support on streams.

Instances of this class represent a “compiled” XPath expression, and provide methods for testing the path against a stream, as well as extracting a substream matching that path.

select(stream, namespaces=None, variables=None)

Returns a substream of the given stream that matches the path.

If there are no matches, this method returns an empty stream.

>>> from genshi.input import XML
>>> xml = XML('<root><elem><child>Text</child></elem></root>')

>>> print(Path('.//child').select(xml))
<child>Text</child>

>>> print(Path('.//child/text()').select(xml))
Text

Parameters:

• stream – the stream to select from
• namespaces – (optional) a mapping of namespace prefixes to URIs
• variables – (optional) a mapping of variable names to values

Returns:

the substream matching the path, or an empty stream

Return type:

Stream

test(ignore_context=False)

Returns a function that can be used to track whether the path matches a specific stream event.

The function returned expects the positional arguments event, namespaces and variables. The first is a stream event, while the latter two are a mapping of namespace prefixes to URIs, and a mapping of variable names to values, respectively. In addition, the function accepts an updateonly keyword argument that default to False. If it is set to True, the function only updates its internal state, but does not perform any tests or return a result.

If the path matches the event, the function returns the match (for example, a START or TEXT event.) Otherwise, it returns None.

>>> from genshi.input import XML
>>> xml = XML('<root><elem><child id="1"/></elem><child id="2"/></root>')
>>> test = Path('child').test()
>>> namespaces, variables = {}, {}
>>> for event in xml:
...     if test(event, namespaces, variables):
...         print('%s %r' % (event[0], event[1]))
START (QName('child'), Attrs([(QName('id'), u'2')]))

Parameters:ignore_context – if True, the path is interpreted like a pattern in XSLT, meaning for example that it will match at any depth Returns:a function that can be used to test individual events in a stream against the path Return type:function

exception genshi.path.PathSyntaxError(message, filename=None, lineno=-1, offset=-1)

Exception raised when an XPath expression is syntactically incorrect.