Edgewall Software

ApiDocs/genshi.builder

Version 3 (modified by cmlenz, 8 years ago)

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genshi.builder

Support for programmatically generating markup streams from Python code using a very simple syntax. The main entry point to this module is the tag object (which is actually an instance of the ElementFactory class). You should rarely (if ever) need to directly import and use any of the other classes in this module.

Elements can be created using the tag object using attribute access. For example:

>>> doc = tag.p('Some text and ', tag.a('a link', href='http://example.org/'), '.')
>>> doc
<Element "p">

This produces an Element instance which can be further modified to add child nodes and attributes. This is done by "calling" the element: positional arguments are added as child nodes (alternatively, the Element.append method can be used for that purpose), whereas keywords arguments are added as attributes:

>>> doc(tag.br)
<Element "p">
>>> print(doc)
<p>Some text and <a href="http://example.org/">a link</a>.<br/></p>

If an attribute name collides with a Python keyword, simply append an underscore to the name:

>>> doc(class_='intro')
<Element "p">
>>> print(doc)
<p class="intro">Some text and <a href="http://example.org/">a link</a>.<br/></p>

As shown above, an Element can easily be directly rendered to XML text by printing it or using the Python str() function. This is basically a shortcut for converting the Element to a stream and serializing that stream:

>>> stream = doc.generate()
>>> stream #doctest: +ELLIPSIS
<genshi.core.Stream object at ...>
>>> print(stream)
<p class="intro">Some text and <a href="http://example.org/">a link</a>.<br/></p>

The tag object also allows creating "fragments", which are basically lists of nodes (elements or text) that don't have a parent element. This can be useful for creating snippets of markup that are attached to a parent element later (for example in a template). Fragments are created by calling the tag object, which returns an object of type Fragment:

>>> fragment = tag('Hello, ', tag.em('world'), '!')
>>> fragment
<Fragment>
>>> print(fragment)
Hello, <em>world</em>!

Fragment

Represents a markup fragment, which is basically just a list of element or text nodes.

append(self, node)

Append an element or string as child node.

param node:the node to append; can be an Element, Fragment, or a Stream, or a Python string or number

generate(self)

Return a markup event stream for the fragment.

rtype:Stream

Element

Simple XML output generator based on the builder pattern.

Construct XML elements by passing the tag name to the constructor:

>>> print(Element('strong'))
<strong/>

Attributes can be specified using keyword arguments. The values of the arguments will be converted to strings and any special XML characters escaped:

>>> print(Element('textarea', rows=10))
<textarea rows="10"/>
>>> print(Element('span', title='1 < 2'))
<span title="1 &lt; 2"/>
>>> print(Element('span', title='"baz"'))
<span title="&#34;baz&#34;"/>

The " character is escaped using a numerical entity. The order in which attributes are rendered is undefined.

If an attribute value evaluates to None, that attribute is not included in the output:

>>> print(Element('a', name=None))
<a/>

Attribute names that conflict with Python keywords can be specified by appending an underscore:

>>> print(Element('div', class_='warning'))
<div class="warning"/>

Nested elements can be added to an element using item access notation. The call notation can also be used for this and for adding attributes using keyword arguments, as one would do in the constructor.

>>> print(Element('ul')(Element('li'), Element('li')))
<ul><li/><li/></ul>
>>> print(Element('a')('Label'))
<a>Label</a>
>>> print(Element('a')('Label', href="target"))
<a href="target">Label</a>

Text nodes can be nested in an element by adding strings instead of elements. Any special characters in the strings are escaped automatically:

>>> print(Element('em')('Hello world'))
<em>Hello world</em>
>>> print(Element('em')(42))
<em>42</em>
>>> print(Element('em')('1 < 2'))
<em>1 &lt; 2</em>

This technique also allows mixed content:

>>> print(Element('p')('Hello ', Element('b')('world')))
<p>Hello <b>world</b></p>

Quotes are not escaped inside text nodes: >>> print(Element('p')('"Hello"')) <p>"Hello"</p>

Elements can also be combined with other elements or strings using the addition operator, which results in a Fragment object that contains the operands:

>>> print(Element('br') + 'some text' + Element('br'))
<br/>some text<br/>

Elements with a namespace can be generated using the Namespace and/or QName classes:

>>> from genshi.core import Namespace
>>> xhtml = Namespace('http://www.w3.org/1999/xhtml')
>>> print(Element(xhtml.html, lang='en'))
<html xmlns="http://www.w3.org/1999/xhtml" lang="en"/>

generate(self)

Return a markup event stream for the fragment.

rtype:Stream

ElementFactory

Factory for Element objects.

A new element is created simply by accessing a correspondingly named attribute of the factory object:

>>> factory = ElementFactory()
>>> print(factory.foo)
<foo/>
>>> print(factory.foo(id=2))
<foo id="2"/>

Markup fragments (lists of nodes without a parent element) can be created by calling the factory:

>>> print(factory('Hello, ', factory.em('world'), '!'))
Hello, <em>world</em>!

A factory can also be bound to a specific namespace:

>>> factory = ElementFactory('http://www.w3.org/1999/xhtml')
>>> print(factory.html(lang="en"))
<html xmlns="http://www.w3.org/1999/xhtml" lang="en"/>

The namespace for a specific element can be altered on an existing factory by specifying the new namespace using item access:

>>> factory = ElementFactory()
>>> print(factory.html(factory['http://www.w3.org/2000/svg'].g(id=3)))
<html><g xmlns="http://www.w3.org/2000/svg" id="3"/></html>

Usually, the ElementFactory class is not be used directly. Rather, the tag instance should be used to create elements.


See ApiDocs, Documentation