Mercurial > genshi > genshi-test
annotate doc/xml-templates.txt @ 283:5cbeeb72c5d4
Fix regression introduced in [333:334]: includes no longer used the search path, because the loader was always seeing an absolute path.
| author | cmlenz |
|---|---|
| date | Thu, 12 Oct 2006 12:23:38 +0000 |
| parents | 4afa86e2ad83 |
| children | 7ae694e7462e |
| rev | line source |
|---|---|
| 226 | 1 .. -*- mode: rst; encoding: utf-8 -*- |
| 2 | |
| 3 ============================ | |
| 230 | 4 Genshi XML Template Language |
| 226 | 5 ============================ |
| 6 | |
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7 Genshi provides a XML-based template language that is heavily inspired by Kid_, |
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8 which in turn was inspired by a number of existing template languages, namely |
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9 XSLT_, TAL_, and PHP_. |
| 226 | 10 |
| 11 .. _kid: http://kid-templating.org/ | |
| 12 .. _python: http://www.python.org/ | |
| 13 .. _xslt: http://www.w3.org/TR/xslt | |
| 14 .. _tal: http://www.zope.org/Wikis/DevSite/Projects/ZPT/TAL | |
| 15 .. _php: http://www.php.net/ | |
| 16 | |
| 17 This document describes the template language and will be most useful as | |
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18 reference to those developing Genshi XML templates. Templates are XML files of |
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19 some kind (such as XHTML) that include processing directives_ (elements or |
| 226 | 20 attributes identified by a separate namespace) that affect how the template is |
| 21 rendered, and template expressions_ that are dynamically substituted by | |
| 22 variable data. | |
| 23 | |
| 24 | |
| 25 .. contents:: Contents | |
| 26 :depth: 3 | |
| 27 .. sectnum:: | |
| 28 | |
| 29 ---------- | |
| 30 Python API | |
| 31 ---------- | |
| 32 | |
| 230 | 33 The Python code required for templating with Genshi is generally based on the |
| 226 | 34 following pattern: |
| 35 | |
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36 * Attain a ``MarkupTemplate`` object from a string or file object containing |
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37 the template XML source. This can either be done directly, or through a |
| 226 | 38 ``TemplateLoader`` instance. |
| 39 * Call the ``generate()`` method of the template, passing any data that should | |
| 40 be made available to the template as keyword arguments. | |
| 41 * Serialize the resulting stream using its ``render()`` method. | |
| 42 | |
| 43 For example:: | |
| 44 | |
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45 from genshi.template import MarkupTemplate |
| 226 | 46 |
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47 tmpl = MarkupTemplate('<h1>$title</h1>') |
| 226 | 48 stream = tmpl.generate(title='Hello, world!') |
| 49 print stream.render('xhtml') | |
| 50 | |
| 51 That code would produce the following output:: | |
| 52 | |
| 53 <h1>Hello, world!</h1> | |
| 54 | |
| 55 However, if you want includes_ to work, you should attain the template instance | |
| 56 through a ``TemplateLoader``, and load the template from a file:: | |
| 57 | |
| 230 | 58 from genshi.template import TemplateLoader |
| 226 | 59 |
| 60 loader = TemplateLoader([templates_dir]) | |
| 61 tmpl = loader.load('test.html') | |
| 62 stream = tmpl.generate(title='Hello, world!') | |
| 63 print stream.render('xhtml') | |
| 64 | |
| 65 | |
| 66 .. _`expressions`: | |
| 67 | |
| 68 -------------------- | |
| 69 Template Expressions | |
| 70 -------------------- | |
| 71 | |
| 72 Python_ expressions can be used in text and attribute values. An expression is | |
| 73 substituted with the result of its evaluation against the template data. | |
| 74 Expressions need to prefixed with a dollar sign (``$``) and usually enclosed in | |
| 75 curly braces (``{…}``). | |
| 76 | |
| 77 If the expression starts with a letter and contains only letters and digits, | |
| 78 the curly braces may be omitted. In all other cases, the braces are required so | |
| 79 that the template processors knows where the expression ends:: | |
| 80 | |
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81 >>> from genshi.template import MarkupTemplate |
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82 >>> tmpl = MarkupTemplate('<em>${items[0].capitalize()} item</em>') |
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83 >>> print tmpl.generate(items=['first', 'second']) |
| 226 | 84 <em>First item</em> |
| 85 | |
| 86 Expressions support the full power of Python. In addition, it is possible to | |
| 87 access items in a dictionary using “dotted notation” (i.e. as if they were | |
| 88 attributes), and vice-versa (i.e. access attributes as if they were items in a | |
| 89 dictionary):: | |
| 90 | |
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91 >>> from genshi.template import MarkupTemplate |
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92 >>> tmpl = MarkupTemplate('<em>${dict.foo}</em>') |
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93 >>> print tmpl.generate(dict={'foo': 'bar'}) |
| 226 | 94 <em>bar</em> |
| 95 | |
| 244 | 96 Another difference is that you can access variables that are not defined, and |
| 97 won't get a ``NameError`` exception:: | |
| 98 | |
| 99 >>> from genshi.template import TextTemplate | |
| 100 >>> tmpl = TextTemplate('${doh}') | |
| 101 >>> print tmpl.generate() | |
| 102 <BLANKLINE> | |
| 103 | |
| 104 You **will** however get a ``NameError`` if you try to call an undefined | |
| 105 variable, or do anything else with it, such as accessing its attributes. If you | |
| 106 need to know whether a variable is defined, you can check its type against the | |
| 107 ``Undefined`` class, for example in an `py:if`_ directive:: | |
| 108 | |
| 109 >>> from genshi.template import TextTemplate | |
| 110 >>> tmpl = TextTemplate('${type(doh) is Undefined}') | |
| 111 >>> print tmpl.generate() | |
| 112 True | |
| 113 | |
| 226 | 114 |
| 115 .. _`directives`: | |
| 116 | |
| 117 ------------------- | |
| 118 Template Directives | |
| 119 ------------------- | |
| 120 | |
| 121 Directives are elements and/or attributes in the template that are identified | |
| 230 | 122 by the namespace ``http://genshi.edgewall.org/``. They can affect how the |
| 123 template is rendered in a number of ways: Genshi provides directives for | |
| 226 | 124 conditionals and looping, among others. |
| 125 | |
| 126 To use directives in a template, the namespace should be declared, which is | |
| 127 usually done on the root element:: | |
| 128 | |
| 129 <html xmlns="http://www.w3.org/1999/xhtml" | |
| 230 | 130 xmlns:py="http://genshi.edgewall.org/" |
| 226 | 131 lang="en"> |
| 132 ... | |
| 133 </html> | |
| 134 | |
| 135 In this example, the default namespace is set to the XHTML namespace, and the | |
| 230 | 136 namespace for Genshi directives is bound to the prefix “py”. |
| 226 | 137 |
| 138 All directives can be applied as attributes, and some can also be used as | |
| 139 elements. The ``if`` directives for conditionals, for example, can be used in | |
| 140 both ways:: | |
| 141 | |
| 142 <html xmlns="http://www.w3.org/1999/xhtml" | |
| 230 | 143 xmlns:py="http://genshi.edgewall.org/" |
| 226 | 144 lang="en"> |
| 145 ... | |
| 146 <div py:if="foo"> | |
| 147 <p>Bar</p> | |
| 148 </div> | |
| 149 ... | |
| 150 </html> | |
| 151 | |
| 152 This is basically equivalent to the following:: | |
| 153 | |
| 154 <html xmlns="http://www.w3.org/1999/xhtml" | |
| 230 | 155 xmlns:py="http://genshi.edgewall.org/" |
| 226 | 156 lang="en"> |
| 157 ... | |
| 158 <py:if test="foo"> | |
| 159 <div> | |
| 160 <p>Bar</p> | |
| 161 </div> | |
| 162 </py:if> | |
| 163 ... | |
| 164 </html> | |
| 165 | |
| 166 The rationale behind the second form is that directives do not always map | |
| 167 naturally to elements in the template. In such cases, the ``py:strip`` | |
| 168 directive can be used to strip off the unwanted element, or the directive can | |
| 169 simply be used as an element. | |
| 170 | |
| 171 | |
| 237 | 172 Conditional Sections |
| 226 | 173 ==================== |
| 174 | |
| 235 | 175 .. _`py:if`: |
| 226 | 176 |
| 235 | 177 ``py:if`` |
| 237 | 178 --------- |
| 226 | 179 |
| 235 | 180 The element is only rendered if the expression evaluates to a truth value:: |
| 226 | 181 |
| 235 | 182 <div> |
| 183 <b py:if="foo">${bar}</b> | |
| 184 </div> | |
| 226 | 185 |
| 235 | 186 Given the data ``foo=True`` and ``bar='Hello'`` in the template context, this |
| 187 would produce:: | |
| 188 | |
| 189 <div> | |
| 190 <b>Hello</b> | |
| 191 </div> | |
| 192 | |
| 193 This directive can also be used as an element:: | |
| 194 | |
| 195 <div> | |
| 196 <py:if test="foo"> | |
| 197 <b>${bar}</b> | |
| 198 </py:if> | |
| 199 </div> | |
| 226 | 200 |
| 201 .. _`py:choose`: | |
| 202 .. _`py:when`: | |
| 203 .. _`py:otherwise`: | |
| 204 | |
| 237 | 205 ``py:choose`` |
| 206 ------------- | |
| 226 | 207 |
| 237 | 208 The ``py:choose`` directive, in combination with the directives ``py:when`` |
| 209 and ``py:otherwise`` provides advanced contional processing for rendering one | |
| 226 | 210 of several alternatives. The first matching ``py:when`` branch is rendered, or, |
| 211 if no ``py:when`` branch matches, the ``py:otherwise`` branch is be rendered. | |
| 212 | |
| 213 If the ``py:choose`` directive is empty the nested ``py:when`` directives will | |
| 214 be tested for truth:: | |
| 215 | |
| 216 <div py:choose=""> | |
| 217 <span py:when="0 == 1">0</span> | |
| 218 <span py:when="1 == 1">1</span> | |
| 219 <span py:otherwise="">2</span> | |
| 220 </div> | |
| 221 | |
| 222 This would produce the following output:: | |
| 223 | |
| 224 <div> | |
| 225 <span>1</span> | |
| 226 </div> | |
| 227 | |
| 228 If the ``py:choose`` directive contains an expression the nested ``py:when`` | |
| 229 directives will be tested for equality to the parent ``py:choose`` value:: | |
| 230 | |
| 231 <div py:choose="1"> | |
| 232 <span py:when="0">0</span> | |
| 233 <span py:when="1">1</span> | |
| 234 <span py:otherwise="">2</span> | |
| 235 </div> | |
| 236 | |
| 237 This would produce the following output:: | |
| 238 | |
| 239 <div> | |
| 240 <span>1</span> | |
| 241 </div> | |
| 242 | |
| 243 | |
| 235 | 244 Looping |
| 237 | 245 ======= |
| 226 | 246 |
| 235 | 247 .. _`py:for`: |
| 226 | 248 |
| 235 | 249 ``py:for`` |
| 237 | 250 ---------- |
| 235 | 251 |
| 252 The element is repeated for every item in an iterable:: | |
| 226 | 253 |
| 254 <ul> | |
| 235 | 255 <li py:for="item in items">${item}</li> |
| 226 | 256 </ul> |
| 257 | |
| 235 | 258 Given ``items=[1, 2, 3]`` in the context data, this would produce:: |
| 226 | 259 |
| 260 <ul> | |
| 235 | 261 <li>1</li><li>2</li><li>3</li> |
| 226 | 262 </ul> |
| 263 | |
| 235 | 264 This directive can also be used as an element:: |
| 226 | 265 |
| 235 | 266 <ul> |
| 267 <py:for each="item in items"> | |
| 268 <li>${item}</li> | |
| 269 </py:for> | |
| 270 </ul> | |
| 271 | |
| 272 | |
| 273 Snippet Reuse | |
| 237 | 274 ============= |
| 226 | 275 |
| 276 .. _`py:def`: | |
| 277 .. _`macros`: | |
| 278 | |
| 279 ``py:def`` | |
| 237 | 280 ---------- |
| 226 | 281 |
| 282 The ``py:def`` directive can be used to create macros, i.e. snippets of | |
| 283 template code that have a name and optionally some parameters, and that can be | |
| 284 inserted in other places:: | |
| 285 | |
| 286 <div> | |
| 287 <p py:def="greeting(name)" class="greeting"> | |
| 288 Hello, ${name}! | |
| 289 </p> | |
| 290 ${greeting('world')} | |
| 291 ${greeting('everyone else')} | |
| 292 </div> | |
| 293 | |
| 294 The above would be rendered to:: | |
| 295 | |
| 296 <div> | |
| 297 <p class="greeting"> | |
| 298 Hello, world! | |
| 299 </p> | |
| 300 <p class="greeting"> | |
| 301 Hello, everyone else! | |
| 302 </p> | |
| 303 </div> | |
| 304 | |
| 305 If a macro doesn't require parameters, it can be defined as well as called | |
| 306 without the parenthesis. For example:: | |
| 307 | |
| 308 <div> | |
| 309 <p py:def="greeting" class="greeting"> | |
| 310 Hello, world! | |
| 311 </p> | |
| 312 ${greeting} | |
| 313 </div> | |
| 314 | |
| 315 The above would be rendered to:: | |
| 316 | |
| 317 <div> | |
| 318 <p class="greeting"> | |
| 319 Hello, world! | |
| 320 </p> | |
| 321 </div> | |
| 322 | |
| 323 This directive can also be used as an element:: | |
| 324 | |
| 325 <div> | |
| 326 <py:def function="greeting(name)"> | |
| 327 <p class="greeting">Hello, ${name}!</p> | |
| 328 </py:def> | |
| 329 </div> | |
| 330 | |
| 331 | |
| 235 | 332 .. _Match Templates: |
| 226 | 333 .. _`py:match`: |
| 334 | |
| 335 ``py:match`` | |
| 237 | 336 ------------ |
| 226 | 337 |
| 338 This directive defines a *match template*: given an XPath expression, it | |
| 339 replaces any element in the template that matches the expression with its own | |
| 340 content. | |
| 341 | |
| 342 For example, the match template defined in the following template matches any | |
| 343 element with the tag name “greeting”:: | |
| 344 | |
| 345 <div> | |
| 346 <span py:match="greeting"> | |
| 347 Hello ${select('@name')} | |
| 348 </span> | |
| 349 <greeting name="Dude" /> | |
| 350 </div> | |
| 351 | |
| 352 This would result in the following output:: | |
| 353 | |
| 354 <div> | |
| 355 <span> | |
| 356 Hello Dude | |
| 357 </span> | |
| 358 </div> | |
| 359 | |
| 360 Inside the body of a ``py:match`` directive, the ``select(path)`` function is | |
| 361 made available so that parts or all of the original element can be incorporated | |
| 230 | 362 in the output of the match template. See [wiki:GenshiStream#UsingXPath] for |
| 226 | 363 more information about this function. |
| 364 | |
| 365 This directive can also be used as an element:: | |
| 366 | |
| 367 <div> | |
| 368 <py:match path="greeting"> | |
| 369 <span>Hello ${select('@name')}</span> | |
| 370 </py:match> | |
| 371 <greeting name="Dude" /> | |
| 372 </div> | |
| 373 | |
| 374 | |
| 235 | 375 Variable Binding |
| 237 | 376 ================ |
| 226 | 377 |
| 378 .. _`with`: | |
| 379 | |
| 380 ``py:with`` | |
| 237 | 381 ----------- |
| 226 | 382 |
| 383 The ``py:with`` directive lets you assign expressions to variables, which can | |
| 384 be used to make expressions inside the directive less verbose and more | |
| 385 efficient. For example, if you need use the expression ``author.posts`` more | |
| 386 than once, and that actually results in a database query, assigning the results | |
| 387 to a variable using this directive would probably help. | |
| 388 | |
| 389 For example:: | |
| 390 | |
| 391 <div> | |
| 392 <span py:with="y=7; z=x+10">$x $y $z</span> | |
| 393 </div> | |
| 394 | |
| 395 Given ``x=42`` in the context data, this would produce:: | |
| 396 | |
| 397 <div> | |
| 398 <span>42 7 52</span> | |
| 399 </div> | |
| 400 | |
| 401 This directive can also be used as an element:: | |
| 402 | |
| 403 <div> | |
| 404 <py:with vars="y=7; z=x+10">$x $y $z</py:with> | |
| 405 </div> | |
| 406 | |
| 407 Note that if a variable of the same name already existed outside of the scope | |
| 408 of the ``py:with`` directive, it will **not** be overwritten. Instead, it | |
| 409 will have the same value it had prior to the ``py:with`` assignment. | |
| 230 | 410 Effectively, this means that variables are immutable in Genshi. |
| 226 | 411 |
| 412 | |
| 235 | 413 Structure Manipulation |
| 237 | 414 ====================== |
| 235 | 415 |
| 416 .. _`py:attrs`: | |
| 417 | |
| 418 ``py:attrs`` | |
| 237 | 419 ------------ |
| 235 | 420 |
| 421 This directive adds, modifies or removes attributes from the element:: | |
| 422 | |
| 423 <ul> | |
| 424 <li py:attrs="foo">Bar</li> | |
| 425 </ul> | |
| 426 | |
| 427 Given ``foo={'class': 'collapse'}`` in the template context, this would | |
| 428 produce:: | |
| 429 | |
| 430 <ul> | |
| 431 <li class="collapse">Bar</li> | |
| 432 </ul> | |
| 433 | |
| 434 Attributes with the value ``None`` are omitted, so given ``foo={'class': None}`` | |
| 435 in the context for the same template this would produce:: | |
| 436 | |
| 437 <ul> | |
| 438 <li>Bar</li> | |
| 439 </ul> | |
| 440 | |
| 441 This directive can only be used as an attribute. | |
| 442 | |
| 443 | |
| 444 .. _`py:content`: | |
| 445 | |
| 446 ``py:content`` | |
| 237 | 447 -------------- |
| 235 | 448 |
| 449 This directive replaces any nested content with the result of evaluating the | |
| 450 expression:: | |
| 451 | |
| 452 <ul> | |
| 453 <li py:content="bar">Hello</li> | |
| 454 </ul> | |
| 455 | |
| 456 Given ``bar='Bye'`` in the context data, this would produce:: | |
| 457 | |
| 458 <ul> | |
| 459 <li>Bye</li> | |
| 460 </ul> | |
| 461 | |
| 462 This directive can only be used as an attribute. | |
| 463 | |
| 464 | |
| 465 .. _`py:replace`: | |
| 466 | |
| 467 ``py:replace`` | |
| 237 | 468 -------------- |
| 235 | 469 |
| 470 This directive replaces the element itself with the result of evaluating the | |
| 471 expression:: | |
| 472 | |
| 473 <div> | |
| 474 <span py:replace="bar">Hello</span> | |
| 475 </div> | |
| 476 | |
| 477 Given ``bar='Bye'`` in the context data, this would produce:: | |
| 478 | |
| 479 <div> | |
| 480 Bye | |
| 481 </div> | |
| 482 | |
| 483 This directive can only be used as an attribute. | |
| 484 | |
| 485 | |
| 486 .. _`py:strip`: | |
| 487 | |
| 488 ``py:strip`` | |
| 237 | 489 ------------ |
| 235 | 490 |
| 491 This directive conditionally strips the top-level element from the output. When | |
| 492 the value of the ``py:strip`` attribute evaluates to ``True``, the element is | |
| 493 stripped from the output:: | |
| 494 | |
| 495 <div> | |
| 496 <div py:strip="True"><b>foo</b></div> | |
| 497 </div> | |
| 498 | |
| 499 This would be rendered as:: | |
| 500 | |
| 501 <div> | |
| 502 <b>foo</b> | |
| 503 </div> | |
| 504 | |
| 505 As a shorthand, if the value of the ``py:strip`` attribute is empty, that has | |
| 506 the same effect as using a truth value (i.e. the element is stripped). | |
| 507 | |
| 508 | |
| 226 | 509 .. _order: |
| 510 | |
| 511 Processing Order | |
| 512 ================ | |
| 513 | |
| 514 It is possible to attach multiple directives to a single element, although not | |
| 515 all combinations make sense. When multiple directives are encountered, they are | |
| 516 processed in the following order: | |
| 517 | |
| 518 #. `py:def`_ | |
| 519 #. `py:match`_ | |
| 520 #. `py:when`_ | |
| 521 #. `py:otherwise`_ | |
| 522 #. `py:for`_ | |
| 523 #. `py:if`_ | |
| 524 #. `py:choose`_ | |
| 525 #. `py:with`_ | |
| 526 #. `py:replace`_ | |
| 527 #. `py:content`_ | |
| 528 #. `py:attrs`_ | |
| 529 #. `py:strip`_ | |
| 530 | |
| 531 | |
| 532 .. _includes: | |
| 533 | |
| 534 -------- | |
| 535 Includes | |
| 536 -------- | |
| 537 | |
| 538 To reuse common snippets of template code, you can include other files using | |
| 539 XInclude_. | |
| 540 | |
| 541 .. _xinclude: http://www.w3.org/TR/xinclude/ | |
| 542 | |
| 543 For this, you need to declare the XInclude namespace (commonly bound to the | |
| 544 prefix “xi”) and use the ``<xi:include>`` element where you want the external | |
| 545 file to be pulled in:: | |
| 546 | |
| 547 <html xmlns="http://www.w3.org/1999/xhtml" | |
| 230 | 548 xmlns:py="http://genshi.edgewall.org/" |
| 226 | 549 xmlns:xi="http://www.w3.org/2001/XInclude"> |
| 550 <xi:include href="base.html" /> | |
| 551 ... | |
| 552 </html> | |
| 553 | |
| 554 Include paths are relative to the filename of the template currently being | |
| 555 processed. So if the example above was in the file "``myapp/index.html``" | |
| 556 (relative to the template search path), the XInclude processor would look for | |
| 557 the included file at "``myapp/base.html``". You can also use Unix-style | |
| 558 relative paths, for example "``../base.html``" to look in the parent directory. | |
| 559 | |
| 560 Any content included this way is inserted into the generated output instead of | |
| 561 the ``<xi:include>`` element. The included template sees the same context data. | |
| 562 `Match templates`_ and `macros`_ in the included template are also available to | |
| 563 the including template after the point it was included. | |
| 564 | |
| 565 By default, an error will be raised if an included file is not found. If that's | |
| 566 not what you want, you can specify fallback content that should be used if the | |
| 567 include fails. For example, to to make the include above fail silently, you'd | |
| 273 | 568 write:: |
| 226 | 569 |
| 570 <xi:include href="base.html"><xi:fallback /></xi:include> | |
| 571 | |
| 273 | 572 See the `XInclude specification`_ for more about fallback content. Note though |
| 573 that Genshi currently only supports a small subset of XInclude. | |
| 574 | |
| 575 .. _`xinclude specification`: http://www.w3.org/TR/xinclude/ | |
| 226 | 576 |
| 230 | 577 Incudes in Genshi are fully dynamic: Just like normal attributes, the `href` |
| 226 | 578 attribute accepts expressions_, and directives_ can be used on the |
| 579 ``<xi:include />`` element just as on any other element, meaning you can do | |
| 580 things like conditional includes:: | |
| 581 | |
| 582 <xi:include href="${name}.html" py:if="not in_popup" | |
| 583 py:for="name in ('foo', 'bar', 'baz')" /> | |
| 584 | |
| 585 | |
| 586 .. _comments: | |
| 587 | |
| 588 -------- | |
| 589 Comments | |
| 590 -------- | |
| 591 | |
| 592 Normal XML/HTML comment syntax can be used in templates:: | |
| 593 | |
| 594 <!-- this is a comment --> | |
| 595 | |
| 596 However, such comments get passed through the processing pipeline and are by | |
| 597 default included in the final output. If that's not desired, prefix the comment | |
| 598 text with an exclamation mark:: | |
| 599 | |
| 600 <!-- !this is a comment too, but one that will be stripped from the output --> | |
| 601 | |
| 602 Note that it does not matter whether there's whitespace before or after the | |
| 603 exclamation mark, so the above could also be written as follows:: | |
| 604 | |
| 605 <!--! this is a comment too, but one that will be stripped from the output --> |