Mercurial > genshi > mirror
annotate doc/xpath.txt @ 1040:accc8a0cf486 trunk
Add support for iterator arguments to _speedups Markup.join implementation so that it matches the Python implementation (fixes #574).
| author | hodgestar |
|---|---|
| date | Thu, 20 Mar 2014 11:41:43 +0000 |
| parents | f33ecf3c319e |
| children |
| rev | line source |
|---|---|
| 226 | 1 .. -*- mode: rst; encoding: utf-8 -*- |
| 2 | |
| 3 ===================== | |
| 230 | 4 Using XPath in Genshi |
| 226 | 5 ===================== |
| 6 | |
| 230 | 7 Genshi provides basic XPath_ support for matching and querying event streams. |
| 226 | 8 |
| 9 .. _xpath: http://www.w3.org/TR/xpath | |
| 10 | |
| 11 | |
| 12 .. contents:: Contents | |
| 13 :depth: 2 | |
| 14 .. sectnum:: | |
| 15 | |
| 16 | |
| 17 ----------- | |
| 18 Limitations | |
| 19 ----------- | |
| 20 | |
| 230 | 21 Due to the streaming nature of the processing model, Genshi uses only a subset |
| 226 | 22 of the `XPath 1.0`_ language. |
| 23 | |
| 24 .. _`XPath 1.0`: http://www.w3.org/TR/xpath | |
| 25 | |
| 26 In particular, only the following axes are supported: | |
| 27 | |
| 28 * ``attribute`` | |
| 29 * ``child`` | |
| 30 * ``descendant`` | |
| 31 * ``descendant-or-self`` | |
| 32 * ``self`` | |
| 33 | |
| 230 | 34 This means you can't use the ``parent``, ancestor, or sibling axes in Genshi |
| 226 | 35 (the ``namespace`` axis isn't supported either, but what you'd ever need that |
| 36 for I don't know). Basically, any path expression that would require buffering | |
| 37 of the stream is not supported. | |
| 38 | |
| 394 | 39 Predicates are of course supported, but path expressions *inside* predicates |
| 226 | 40 are restricted to attribute lookups (again due to the lack of buffering). |
| 41 | |
| 42 Most of the XPath functions and operators are supported, however they | |
| 43 (currently) only work inside predicates. The following functions are **not** | |
| 44 supported: | |
| 45 | |
| 46 * ``count()`` | |
| 47 * ``id()`` | |
| 48 * ``lang()`` | |
| 49 * ``last()`` | |
| 50 * ``position()`` | |
| 51 * ``string()`` | |
| 52 * ``sum()`` | |
| 53 | |
| 54 The mathematical operators (``+``, ``-``, ``*``, ``div``, and ``mod``) are not | |
| 516 | 55 yet supported, whereas sub-expressions and the various comparison and logical |
| 56 operators should work as expected. | |
| 226 | 57 |
| 58 You can also use XPath variable references (``$var``) inside predicates. | |
| 59 | |
| 60 | |
| 61 ---------------- | |
| 62 Querying Streams | |
| 63 ---------------- | |
| 64 | |
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1bdccd3bda00
Use syntax highlighting on all the other doc pages, too.
cmlenz
parents:
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65 The ``Stream`` class provides a ``select(path)`` function that can be used to |
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1bdccd3bda00
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cmlenz
parents:
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66 retrieve subsets of the stream: |
| 226 | 67 |
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1bdccd3bda00
Use syntax highlighting on all the other doc pages, too.
cmlenz
parents:
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68 .. code-block:: pycon |
| 226 | 69 |
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510
1bdccd3bda00
Use syntax highlighting on all the other doc pages, too.
cmlenz
parents:
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70 >>> from genshi.input import XML |
| 516 | 71 |
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1bdccd3bda00
Use syntax highlighting on all the other doc pages, too.
cmlenz
parents:
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72 >>> doc = XML('''<doc> |
| 516 | 73 ... <items count="4"> |
| 74 ... <item status="new"> | |
| 75 ... <summary>Foo</summary> | |
| 76 ... </item> | |
| 77 ... <item status="closed"> | |
| 78 ... <summary>Bar</summary> | |
| 79 ... </item> | |
| 80 ... <item status="closed" resolution="invalid"> | |
| 81 ... <summary>Baz</summary> | |
| 82 ... </item> | |
| 83 ... <item status="closed" resolution="fixed"> | |
| 84 ... <summary>Waz</summary> | |
| 85 ... </item> | |
| 86 ... </items> | |
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510
1bdccd3bda00
Use syntax highlighting on all the other doc pages, too.
cmlenz
parents:
394
diff
changeset
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87 ... </doc>''') |
| 516 | 88 |
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f33ecf3c319e
Convert a bunch of print statements to py3k compatible syntax.
cmlenz
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89 >>> print(doc.select('items/item[@status="closed" and ' |
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f33ecf3c319e
Convert a bunch of print statements to py3k compatible syntax.
cmlenz
parents:
516
diff
changeset
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90 ... '(@resolution="invalid" or not(@resolution))]/summary/text()')) |
| 516 | 91 BarBaz |
| 92 | |
| 226 | 93 |
| 94 | |
| 95 --------------------- | |
| 96 Matching in Templates | |
| 97 --------------------- | |
| 98 | |
| 99 See the directive ``py:match`` in the `XML Template Language Specification`_. | |
| 100 | |
| 101 .. _`XML Template Language Specification`: xml-templates.html |