XML writing tools for Python

StackOverflow https://stackoverflow.com/questions/56229

  •  09-06-2019
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Question

I'm currently trying ElementTree and it looks fine, it escapes HTML entities and so on and so forth. Am I missing something truly wonderful I haven't heard of?

This is similar to what I'm actually doing:

import xml.etree.ElementTree as ET
root = ET.Element('html')
head = ET.SubElement(root,'head')
script = ET.SubElement(head,'script')
script.set('type','text/javascript')
script.text = "var a = 'I love á letters'"
body = ET.SubElement(root,'body')
h1 = ET.SubElement(body,'h1')
h1.text = "And I like the fact that 3 > 1"
tree = ET.ElementTree(root)
tree.write('foo.xhtml')

# more foo.xhtml
<html><head><script type="text/javascript">var a = 'I love &amp;aacute;
letters'</script></head><body><h1>And I like the fact that 3 &gt; 1</h1>
</body></html>
Was it helpful?

Solution

I assume that you're actually creating an XML DOM tree, because you want to validate that what goes into this file is valid XML, since otherwise you'd just write a static string to a file. If validating your output is indeed your goal, then I'd suggest

from xml.dom.minidom import parseString

doc = parseString("""<html>
    <head>
        <script type="text/javascript">
            var a = 'I love &amp;aacute; letters'
        </script>
    </head>
    <body>
        <h1>And I like the fact that 3 &gt; 1</h1>
    </body>
    </html>""")

with open("foo.xhtml", "w") as f:
    f.write( doc.toxml() )

This lets you just write the XML you want to output, validate that it's correct (since parseString will raise an exception if it's invalid) and have your code look much nicer.

Presumably you're not just writing the same static XML every time and want some substitution. In this case I'd have lines like

var a = '%(message)s'

and then use the % operator to do the substitution, like

</html>""" % {"message": "I love &amp;aacute; letters"})

OTHER TIPS

Another way is using the E Factory builder from lxml (available in Elementtree too)

>>> from lxml import etree

>>> from lxml.builder import E

>>> def CLASS(*args): # class is a reserved word in Python
...     return {"class":' '.join(args)}

>>> html = page = (
...   E.html(       # create an Element called "html"
...     E.head(
...       E.title("This is a sample document")
...     ),
...     E.body(
...       E.h1("Hello!", CLASS("title")),
...       E.p("This is a paragraph with ", E.b("bold"), " text in it!"),
...       E.p("This is another paragraph, with a", "\n      ",
...         E.a("link", href="http://www.python.org"), "."),
...       E.p("Here are some reserved characters: <spam&egg>."),
...       etree.XML("<p>And finally an embedded XHTML fragment.</p>"),
...     )
...   )
... )

>>> print(etree.tostring(page, pretty_print=True))
<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
      <a href="http://www.python.org">link</a>.</p>
    <p>Here are some reservered characters: &lt;spam&amp;egg&gt;.</p>
    <p>And finally an embedded XHTML fragment.</p>
  </body>
</html>

There's always SimpleXMLWriter, part of the ElementTree toolkit. The interface is dead simple.

Here's an example: 

from elementtree.SimpleXMLWriter import XMLWriter
import sys

w = XMLWriter(sys.stdout)
html = w.start("html")

w.start("head")
w.element("title", "my document")
w.element("meta", name="generator", value="my application 1.0")
w.end()

w.start("body")
w.element("h1", "this is a heading")
w.element("p", "this is a paragraph")

w.start("p")
w.data("this is ")
w.element("b", "bold")
w.data(" and ")
w.element("i", "italic")
w.data(".")
w.end("p")

w.close(html)

https://github.com/galvez/xmlwitch:

import xmlwitch
xml = xmlwitch.Builder(version='1.0', encoding='utf-8')
with xml.feed(xmlns='http://www.w3.org/2005/Atom'):
    xml.title('Example Feed')
    xml.updated('2003-12-13T18:30:02Z')
    with xml.author:
        xml.name('John Doe')
    xml.id('urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6')
    with xml.entry:
        xml.title('Atom-Powered Robots Run Amok')
        xml.id('urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a')
        xml.updated('2003-12-13T18:30:02Z')
        xml.summary('Some text.')
print(xml)

don't you actually want something like:

html(head(script(type='text/javascript', content='var a = ...')),
body(h1('And I like the fact that 3 < 1'), p('just some paragraph'))

I think I saw something like that somewhere. This would be wonderful.

EDIT: Actually, I went and wrote a library today to do just that: magictree

You can use it like this:

from magictree import html, head, script, body, h1, p
root = html(
         head(
           script('''var a = 'I love &amp;aacute; letters''', 
                  type='text/javascript')),
         body(
           h1('And I like the fact that 3 > 1')))

# root is a plain Element object, like those created with ET.Element...
# so you can write it out using ElementTree :)
tree = ET.ElementTree(root)
tree.write('foo.xhtml')

The magic in magictree lies in how the importing works: The Element factories are created when needed. Have a look at the source, it is based on an answer to another StackOverflow question.

I ended up using saxutils.escape(str) to generate valid XML strings and then validating it with Eli's approach to be sure I didn't miss any tag

from xml.sax import saxutils
from xml.dom.minidom import parseString
from xml.parsers.expat import ExpatError

xml = '''<?xml version="1.0" encoding="%s"?>\n
<contents title="%s" crawl_date="%s" in_text_date="%s" 
url="%s">\n<main_post>%s</main_post>\n</contents>''' %
(self.encoding, saxutils.escape(title), saxutils.escape(time), 
saxutils.escape(date), saxutils.escape(url), saxutils.escape(contents))
try:
    minidoc = parseString(xml)
catch ExpatError:
    print "Invalid xml"

For anyone encountering this now, there's actually a way to do this hidden away in Python's standard library in xml.sax.utils.XMLGenerator. Here's an example of it in action:

>>> from xml.sax.saxutils import XMLGenerator
>>> import StringIO
>>> w = XMLGenerator(out, 'utf-8')
>>> w.startDocument()
>>> w.startElement("test", {'bar': 'baz'})
>>> w.characters("Foo")
>>> w.endElement("test")
>>> w.endDocument()
>>> print out.getvalue()
<?xml version="1.0" encoding="utf-8"?>
<test bar="baz">Foo</test>

Try http://uche.ogbuji.net/tech/4suite/amara. It is quite complete and has a straight forward set of access tools. Normal Unicode support, etc. 

#
#Output the XML entry
#
def genFileOLD(out,label,term,idval):
    filename=entryTime() + ".html"
    writer=MarkupWriter(out, indent=u"yes")
    writer.startDocument()
    #Test element and attribute writing
    ans=namespace=u'http://www.w3.org/2005/Atom'
    xns=namespace=u'http://www.w3.org/1999/xhtml'
    writer.startElement(u'entry',
       ans,
       extraNss={u'x':u'http://www.w3.org/1999/xhtml' ,
                 u'dc':u'http://purl.org/dc/elements/1.1'})
    #u'a':u'http://www.w3.org/2005/Atom',
    #writer.attribute(u'xml:lang',unicode("en-UK"))

    writer.simpleElement(u'title',ans,content=unicode(label))
    #writer.simpleElement(u'a:subtitle',ans,content=u' ')
    id=unicode("http://www.dpawson.co.uk/nodesets/"+afn.split(".")[0])
    writer.simpleElement(u'id',ans,content=id)
    writer.simpleElement(u'updated',ans,content=unicode(dtime()))
    writer.startElement(u'author',ans)
    writer.simpleElement(u'name',ans,content=u'Dave ')
    writer.simpleElement(u'uri',ans,
      content=u'http://www.dpawson.co.uk/nodesets/'+afn+".xml")
    writer.endElement(u'author')
    writer.startElement(u'category', ans)
    if (prompt):
        label=unicode(raw_input("Enter label "))
    writer.attribute(u'label',unicode(label))
    if (prompt):
        term = unicode(raw_input("Enter term to use "))
    writer.attribute(u'term', unicode(term))
    writer.endElement(u'category')
    writer.simpleElement(u'rights',ans,content=u'\u00A9 Dave 2005-2008')
    writer.startElement(u'link',ans)
    writer.attribute(u'href',
         unicode("http://www.dpawson.co.uk/nodesets/entries/"+afn+".html"))
    writer.attribute(u'rel',unicode("alternate"))
    writer.endElement(u'link')
    writer.startElement(u'published', ans)
    dt=dtime()
    dtu=unicode(dt)
    writer.text(dtu)
    writer.endElement(u'published')
    writer.simpleElement(u'summary',ans,content=unicode(label))
    writer.startElement(u'content',ans)
    writer.attribute(u'type',unicode("xhtml"))
    writer.startElement(u'div',xns)
    writer.simpleElement(u'h3',xns,content=unicode(label))
    writer.endElement(u'div')
    writer.endElement(u'content')
    writer.endElement(u'entry')
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