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annotate genshi/builder.py @ 433:bc430fd7c54d trunk
More API docs.
| author | cmlenz |
|---|---|
| date | Thu, 22 Mar 2007 21:12:03 +0000 |
| parents | ad01564e87f2 |
| children | 700e7b47bf2b |
| rev | line source |
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| 1 | 1 # -*- coding: utf-8 -*- |
| 2 # | |
| 408 | 3 # Copyright (C) 2006-2007 Edgewall Software |
| 1 | 4 # All rights reserved. |
| 5 # | |
| 6 # This software is licensed as described in the file COPYING, which | |
| 7 # you should have received as part of this distribution. The terms | |
| 230 | 8 # are also available at http://genshi.edgewall.org/wiki/License. |
| 1 | 9 # |
| 10 # This software consists of voluntary contributions made by many | |
| 11 # individuals. For the exact contribution history, see the revision | |
| 230 | 12 # history and logs, available at http://genshi.edgewall.org/log/. |
| 1 | 13 |
| 430 | 14 """Support for programmatically generating markup streams from Python code using |
| 15 a very simple syntax. The main entry point to this module is the `tag` object | |
| 16 (which is actually an instance of the ``ElementFactory`` class). You should | |
| 17 rarely (if ever) need to directly import and use any of the other classes in | |
| 18 this module. | |
| 19 | |
| 20 Elements can be created using the `tag` object using attribute access. For | |
| 21 example: | |
| 22 | |
| 23 >>> doc = tag.p('Some text and ', tag.a('a link', href='http://example.org/'), '.') | |
| 24 >>> doc | |
| 25 <Element "p"> | |
| 26 | |
| 27 This produces an `Element` instance which can be further modified to add child | |
| 28 nodes and attributes. This is done by "calling" the element: positional | |
| 29 arguments are added as child nodes (alternatively, the `Element.append` method | |
| 30 can be used for that purpose), whereas keywords arguments are added as | |
| 31 attributes: | |
| 32 | |
| 33 >>> doc(tag.br) | |
| 34 <Element "p"> | |
| 35 >>> print doc | |
| 36 <p>Some text and <a href="http://example.org/">a link</a>.<br/></p> | |
| 37 | |
| 38 If an attribute name collides with a Python keyword, simply append an underscore | |
| 39 to the name: | |
| 40 | |
| 41 >>> doc(class_='intro') | |
| 42 <Element "p"> | |
| 43 >>> print doc | |
| 44 <p class="intro">Some text and <a href="http://example.org/">a link</a>.<br/></p> | |
| 45 | |
| 46 As shown above, an `Element` can easily be directly rendered to XML text by | |
| 47 printing it or using the Python ``str()`` function. This is basically a | |
| 48 shortcut for converting the `Element` to a stream and serializing that | |
| 49 stream: | |
| 50 | |
| 51 >>> stream = doc.generate() | |
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52 >>> stream #doctest: +ELLIPSIS |
| 430 | 53 <genshi.core.Stream object at ...> |
| 54 >>> print stream | |
| 55 <p class="intro">Some text and <a href="http://example.org/">a link</a>.<br/></p> | |
| 56 | |
| 57 | |
| 58 The `tag` object also allows creating "fragments", which are basically lists | |
| 59 of nodes (elements or text) that don't have a parent element. This can be useful | |
| 60 for creating snippets of markup that are attached to a parent element later (for | |
| 61 example in a template). Fragments are created by calling the `tag` object, which | |
| 62 returns an object of type `Fragment`: | |
| 63 | |
| 64 >>> fragment = tag('Hello, ', tag.em('world'), '!') | |
| 65 >>> fragment | |
| 66 <Fragment> | |
| 67 >>> print fragment | |
| 68 Hello, <em>world</em>! | |
| 69 """ | |
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70 |
| 230 | 71 from genshi.core import Attrs, Namespace, QName, Stream, START, END, TEXT |
| 1 | 72 |
| 433 | 73 __all__ = ['Fragment', 'Element', 'ElementFactory', 'tag'] |
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74 __docformat__ = 'restructuredtext en' |
| 1 | 75 |
| 76 | |
| 77 class Fragment(object): | |
| 28 | 78 """Represents a markup fragment, which is basically just a list of element |
| 79 or text nodes. | |
| 80 """ | |
| 1 | 81 __slots__ = ['children'] |
| 82 | |
| 83 def __init__(self): | |
| 433 | 84 """Create a new fragment.""" |
| 1 | 85 self.children = [] |
| 86 | |
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87 def __add__(self, other): |
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88 return Fragment()(self, other) |
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89 |
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90 def __call__(self, *args): |
| 433 | 91 """Append any positional arguments as child nodes. |
| 92 | |
| 93 :see: `append` | |
| 94 """ | |
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95 map(self.append, args) |
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96 return self |
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97 |
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98 def __iter__(self): |
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99 return self._generate() |
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100 |
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101 def __repr__(self): |
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102 return '<%s>' % self.__class__.__name__ |
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103 |
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104 def __str__(self): |
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105 return str(self.generate()) |
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106 |
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107 def __unicode__(self): |
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108 return unicode(self.generate()) |
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109 |
| 1 | 110 def append(self, node): |
| 433 | 111 """Append an element or string as child node. |
| 112 | |
| 113 :param node: the node to append; can be an `Element`, `Fragment`, or a | |
| 114 `Stream`, or a Python string or number | |
| 115 """ | |
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116 if isinstance(node, (Stream, Element, basestring, int, float, long)): |
| 1 | 117 # For objects of a known/primitive type, we avoid the check for |
| 118 # whether it is iterable for better performance | |
| 119 self.children.append(node) | |
| 120 elif isinstance(node, Fragment): | |
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121 self.children.extend(node.children) |
| 1 | 122 elif node is not None: |
| 123 try: | |
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124 map(self.append, iter(node)) |
| 1 | 125 except TypeError: |
| 126 self.children.append(node) | |
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127 |
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128 def _generate(self): |
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129 for child in self.children: |
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130 if isinstance(child, Fragment): |
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131 for event in child._generate(): |
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132 yield event |
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133 elif isinstance(child, Stream): |
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134 for event in child: |
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135 yield event |
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136 else: |
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137 if not isinstance(child, basestring): |
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138 child = unicode(child) |
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139 yield TEXT, child, (None, -1, -1) |
| 1 | 140 |
| 141 def generate(self): | |
| 28 | 142 """Return a markup event stream for the fragment.""" |
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143 return Stream(self._generate()) |
| 1 | 144 |
| 145 | |
| 345 | 146 def _value_to_unicode(value): |
| 147 if isinstance(value, unicode): | |
| 148 return value | |
| 149 return unicode(value) | |
| 150 | |
| 151 def _kwargs_to_attrs(kwargs): | |
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152 return [(QName(k.rstrip('_').replace('_', '-')), _value_to_unicode(v)) |
| 345 | 153 for k, v in kwargs.items() if v is not None] |
| 154 | |
| 155 | |
| 1 | 156 class Element(Fragment): |
| 157 """Simple XML output generator based on the builder pattern. | |
| 158 | |
| 159 Construct XML elements by passing the tag name to the constructor: | |
| 160 | |
| 161 >>> print Element('strong') | |
| 162 <strong/> | |
| 163 | |
| 164 Attributes can be specified using keyword arguments. The values of the | |
| 165 arguments will be converted to strings and any special XML characters | |
| 166 escaped: | |
| 167 | |
| 168 >>> print Element('textarea', rows=10, cols=60) | |
| 169 <textarea rows="10" cols="60"/> | |
| 170 >>> print Element('span', title='1 < 2') | |
| 171 <span title="1 < 2"/> | |
| 172 >>> print Element('span', title='"baz"') | |
| 173 <span title=""baz""/> | |
| 174 | |
| 175 The " character is escaped using a numerical entity. | |
| 176 The order in which attributes are rendered is undefined. | |
| 177 | |
| 178 If an attribute value evaluates to `None`, that attribute is not included | |
| 179 in the output: | |
| 180 | |
| 181 >>> print Element('a', name=None) | |
| 182 <a/> | |
| 183 | |
| 184 Attribute names that conflict with Python keywords can be specified by | |
| 185 appending an underscore: | |
| 186 | |
| 187 >>> print Element('div', class_='warning') | |
| 188 <div class="warning"/> | |
| 189 | |
| 190 Nested elements can be added to an element using item access notation. | |
| 191 The call notation can also be used for this and for adding attributes | |
| 192 using keyword arguments, as one would do in the constructor. | |
| 193 | |
| 194 >>> print Element('ul')(Element('li'), Element('li')) | |
| 195 <ul><li/><li/></ul> | |
| 196 >>> print Element('a')('Label') | |
| 197 <a>Label</a> | |
| 198 >>> print Element('a')('Label', href="target") | |
| 199 <a href="target">Label</a> | |
| 200 | |
| 201 Text nodes can be nested in an element by adding strings instead of | |
| 202 elements. Any special characters in the strings are escaped automatically: | |
| 203 | |
| 204 >>> print Element('em')('Hello world') | |
| 205 <em>Hello world</em> | |
| 206 >>> print Element('em')(42) | |
| 207 <em>42</em> | |
| 208 >>> print Element('em')('1 < 2') | |
| 209 <em>1 < 2</em> | |
| 210 | |
| 211 This technique also allows mixed content: | |
| 212 | |
| 213 >>> print Element('p')('Hello ', Element('b')('world')) | |
| 214 <p>Hello <b>world</b></p> | |
| 215 | |
| 34 | 216 Quotes are not escaped inside text nodes: |
| 217 >>> print Element('p')('"Hello"') | |
| 218 <p>"Hello"</p> | |
| 219 | |
| 1 | 220 Elements can also be combined with other elements or strings using the |
| 221 addition operator, which results in a `Fragment` object that contains the | |
| 222 operands: | |
| 223 | |
| 224 >>> print Element('br') + 'some text' + Element('br') | |
| 225 <br/>some text<br/> | |
| 226 | |
| 227 Elements with a namespace can be generated using the `Namespace` and/or | |
| 228 `QName` classes: | |
| 229 | |
| 230 | 230 >>> from genshi.core import Namespace |
| 1 | 231 >>> xhtml = Namespace('http://www.w3.org/1999/xhtml') |
| 232 >>> print Element(xhtml.html, lang='en') | |
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233 <html xmlns="http://www.w3.org/1999/xhtml" lang="en"/> |
| 1 | 234 """ |
| 235 __slots__ = ['tag', 'attrib'] | |
| 236 | |
| 237 def __init__(self, tag_, **attrib): | |
| 238 Fragment.__init__(self) | |
| 239 self.tag = QName(tag_) | |
| 345 | 240 self.attrib = Attrs(_kwargs_to_attrs(attrib)) |
| 1 | 241 |
| 242 def __call__(self, *args, **kwargs): | |
| 433 | 243 """Append any positional arguments as child nodes, and keyword arguments |
| 244 as attributes. | |
| 245 | |
| 246 :see: `Fragment.append` | |
| 247 """ | |
| 345 | 248 self.attrib |= Attrs(_kwargs_to_attrs(kwargs)) |
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249 Fragment.__call__(self, *args) |
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250 return self |
| 1 | 251 |
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252 def __repr__(self): |
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253 return '<%s "%s">' % (self.__class__.__name__, self.tag) |
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254 |
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255 def _generate(self): |
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256 yield START, (self.tag, self.attrib), (None, -1, -1) |
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257 for kind, data, pos in Fragment._generate(self): |
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258 yield kind, data, pos |
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259 yield END, self.tag, (None, -1, -1) |
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260 |
| 1 | 261 def generate(self): |
| 28 | 262 """Return a markup event stream for the fragment.""" |
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263 return Stream(self._generate()) |
| 1 | 264 |
| 265 | |
| 266 class ElementFactory(object): | |
| 28 | 267 """Factory for `Element` objects. |
| 268 | |
| 269 A new element is created simply by accessing a correspondingly named | |
| 270 attribute of the factory object: | |
| 271 | |
| 272 >>> factory = ElementFactory() | |
| 273 >>> print factory.foo | |
| 274 <foo/> | |
| 275 >>> print factory.foo(id=2) | |
| 276 <foo id="2"/> | |
| 277 | |
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278 Markup fragments (lists of nodes without a parent element) can be created |
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279 by calling the factory: |
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280 |
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281 >>> print factory('Hello, ', factory.em('world'), '!') |
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282 Hello, <em>world</em>! |
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283 |
| 28 | 284 A factory can also be bound to a specific namespace: |
| 285 | |
| 286 >>> factory = ElementFactory('http://www.w3.org/1999/xhtml') | |
| 287 >>> print factory.html(lang="en") | |
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288 <html xmlns="http://www.w3.org/1999/xhtml" lang="en"/> |
| 28 | 289 |
| 290 The namespace for a specific element can be altered on an existing factory | |
| 291 by specifying the new namespace using item access: | |
| 292 | |
| 293 >>> factory = ElementFactory() | |
| 294 >>> print factory.html(factory['http://www.w3.org/2000/svg'].g(id=3)) | |
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295 <html><g xmlns="http://www.w3.org/2000/svg" id="3"/></html> |
| 28 | 296 |
| 297 Usually, the `ElementFactory` class is not be used directly. Rather, the | |
| 298 `tag` instance should be used to create elements. | |
| 299 """ | |
| 1 | 300 |
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301 def __init__(self, namespace=None): |
| 28 | 302 """Create the factory, optionally bound to the given namespace. |
| 303 | |
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304 :param namespace: the namespace URI for any created elements, or `None` |
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305 for no namespace |
| 28 | 306 """ |
| 20 | 307 if namespace and not isinstance(namespace, Namespace): |
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308 namespace = Namespace(namespace) |
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309 self.namespace = namespace |
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310 |
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311 def __call__(self, *args): |
| 433 | 312 """Create a fragment that has the given positional arguments as child |
| 313 nodes. | |
| 314 | |
| 315 :return: the created `Fragment` | |
| 316 """ | |
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317 return Fragment()(*args) |
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318 |
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319 def __getitem__(self, namespace): |
| 433 | 320 """Return a new factory that is bound to the specified namespace. |
| 321 | |
| 322 :param namespace: the namespace URI or `Namespace` object | |
| 323 :return: an `ElementFactory` that produces elements bound to the given | |
| 324 namespace | |
| 325 """ | |
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326 return ElementFactory(namespace) |
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327 |
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328 def __getattr__(self, name): |
| 433 | 329 """Create an `Element` with the given name. |
| 330 | |
| 331 :param name: the tag name of the element to create | |
| 332 :return: an `Element` with the specified name | |
| 333 """ | |
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334 return Element(self.namespace and self.namespace[name] or name) |
| 1 | 335 |
| 336 | |
| 337 tag = ElementFactory() | |
| 433 | 338 """Global `ElementFactory` bound to the default namespace.""" |