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#
# Element generator factory by Fredrik Lundh.
#
# Source:
# http://online.effbot.org/2006_11_01_archive.htm#et-builder
# http://effbot.python-hosting.com/file/stuff/sandbox/elementlib/builder.py
#
# --------------------------------------------------------------------
# The ElementTree toolkit is
#
# Copyright (c) 1999-2004 by Fredrik Lundh
#
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# and will comply with the following terms and conditions:
#
# Permission to use, copy, modify, and distribute this software and
# its associated documentation for any purpose and without fee is
# hereby granted, provided that the above copyright notice appears in
# all copies, and that both that copyright notice and this permission
# notice appear in supporting documentation, and that the name of
# Secret Labs AB or the author not be used in advertising or publicity
# pertaining to distribution of the software without specific, written
# prior permission.
#
# SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
# TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
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# --------------------------------------------------------------------
"""
The ``E`` Element factory for generating XML documents.
"""
import lxml.etree as ET
from functools import partial
try:
basestring
except NameError:
basestring = str
try:
unicode
except NameError:
unicode = str
class ElementMaker(object):
"""Element generator factory.
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', ...)``::
>>> ET.tostring(E.tag())
'<tag/>'
>>> ET.tostring(E.tag("text"))
'<tag>text</tag>'
>>> ET.tostring(E.tag(E.subtag("text"), "tail"))
'<tag><subtag>text</subtag>tail</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::
>>> E = ElementMaker(namespace="http://my.ns/")
>>> print(ET.tostring( E.test ))
<test xmlns="http://my.ns/"/>
>>> E = ElementMaker(namespace="http://my.ns/", nsmap={'p':'http://my.ns/'})
>>> print(ET.tostring( E.test ))
<p:test xmlns:p="http://my.ns/"/>
"""
def __init__(self, typemap=None,
namespace=None, nsmap=None, makeelement=None):
if namespace is not None:
self._namespace = '{' + namespace + '}'
else:
self._namespace = None
if nsmap:
self._nsmap = dict(nsmap)
else:
self._nsmap = None
if makeelement is not None:
assert callable(makeelement)
self._makeelement = makeelement
else:
self._makeelement = ET.Element
# initialize type map for this element factory
if typemap:
typemap = dict(typemap)
else:
typemap = {}
def add_text(elem, item):
try:
elem[-1].tail = (elem[-1].tail or "") + item
except IndexError:
elem.text = (elem.text or "") + item
def add_cdata(elem, cdata):
if elem.text:
raise ValueError("Can't add a CDATA section. Element already has some text: %r" % elem.text)
elem.text = cdata
if str not in typemap:
typemap[str] = add_text
if unicode not in typemap:
typemap[unicode] = add_text
if ET.CDATA not in typemap:
typemap[ET.CDATA] = add_cdata
def add_dict(elem, item):
attrib = elem.attrib
for k, v in item.items():
if isinstance(v, basestring):
attrib[k] = v
else:
attrib[k] = typemap[type(v)](None, v)
if dict not in typemap:
typemap[dict] = add_dict
self._typemap = typemap
def __call__(self, tag, *children, **attrib):
typemap = self._typemap
if self._namespace is not None and tag[0] != '{':
tag = self._namespace + tag
elem = self._makeelement(tag, nsmap=self._nsmap)
if attrib:
typemap[dict](elem, attrib)
for item in children:
if callable(item):
item = item()
t = typemap.get(type(item))
if t is None:
if ET.iselement(item):
elem.append(item)
continue
for basetype in type(item).__mro__:
# See if the typemap knows of any of this type's bases.
t = typemap.get(basetype)
if t is not None:
break
else:
raise TypeError("bad argument type: %s(%r)" %
(type(item).__name__, item))
v = t(elem, item)
if v:
typemap.get(type(v))(elem, v)
return elem
def __getattr__(self, tag):
return partial(self, tag)
# create factory object
E = ElementMaker()