Unlike the ordinary Element factory, the E factory allows you to pass in
more than just a tag and some optional attributes; you can also pass in
text and other elements. The text is added as either text or tail
attributes, and elements are inserted at the right spot. Some small
examples:
>>> from lxml import etree as ET
>>> from lxml.builder import E
>>> ET.tostring(E("tag"))
'<tag/>'
>>> ET.tostring(E("tag", "text"))
'<tag>text</tag>'
>>> ET.tostring(E("tag", "text", key="value"))
'<tag key="value">text</tag>'
>>> ET.tostring(E("tag", E("subtag", "text"), "tail"))
'<tag><subtag>text</subtag>tail</tag>'
For simple tags, the factory also allows you to write E.tag(...) instead
of E('tag',...):
Here's a somewhat larger example; this shows how to generate HTML
documents, using a mix of prepared factory functions for inline elements,
nested E.tag calls, and embedded XHTML fragments:
# some common inline elements
A = E.a
I = E.i
B = E.b
def CLASS(v):
# helper function, 'class' is a reserved word
return {'class': v}
page = (
E.html(
E.head(
E.title("This is a sample document")
),
E.body(
E.h1("Hello!", CLASS("title")),
E.p("This is a paragraph with ", B("bold"), " text in it!"),
E.p("This is another paragraph, with a ",
A("link", href="http://www.python.org"), "."),
E.p("Here are some reserved characters: <spam&egg>."),
ET.XML("<p>And finally, here is an embedded XHTML fragment.</p>"),
)
)
)
print ET.tostring(page)
Here's a prettyprinted version of the output from the above script:
<html>
<head>
<title>This is a sample document</title>
</head>
<body>
<h1 class="title">Hello!</h1>
<p>This is a paragraph with <b>bold</b> text in it!</p>
<p>This is another paragraph, with <a href="http://www.python.org">link</a>.</p>
<p>Here are some reserved characters: <spam&egg>.</p>
<p>And finally, here is an embedded XHTML fragment.</p>
</body>
</html>
For namespace support, you can pass a namespace map (nsmap)
and/or a specific target namespace to the ElementMaker class: