"Invalid tag name" error when creating element with lxml in python
lxml, python, python-2.7, xml
Solution
You get the error because element names are not allowed to begin with a digit in XML. See http://www.w3.org/TR/xml/#sec-common-syn and http://www.w3.org/TR/xml/#sec-starttags. The first character of a name must be a `NameStartChar`, which disallows digits.
An element such as `<2013-11-30>...</2013-11-30>` is invalid.
An element such as `<D2013-11-30>...</D2013-11-30>` is OK.
If your program is changed to use ElementTree instead of lxml (`from xml.etree import ElementTree as etree` instead of `from lxml import etree`), there is no error. But I would consider that a bug. lxml does the right thing, ElementTree does not.
Problem
I am using lxml to make an xml file and my sample program is : ``` from lxml import etree import datetime dt=datetime.datetime(2013,11,30,4,5,6) dt=dt.strftime('%Y-%m-%d') page=etree.Element('html') doc=etree.ElementTree(page) dateElm=etree.SubElement(page,dt) outfile=open('somefile.xml','w') doc.write(outfile) ``` And I am getting the following error output : ``` dateElm=etree.SubElement(page,dt) File "lxml.etree.pyx", line 2899, in lxml.etree.SubElement (src/lxml/lxml.etree.c:62284) File "apihelpers.pxi", line 171, in lxml.etree._makeSubElement (src/lxml/lxml.etree.c:14296) File "apihelpers.pxi", line 1523, in lxml.etree._tagValidOrRaise (src/lxml/lxml.etree.c:26852) ValueError: Invalid tag name u'2013-11-30' ``` I thought it of a Unicode Error, so tried changing encoding of 'dt' with codes like - `str(dt)` - `unicode(dt).encode('unicode_escape')` - `dt.encocde('ascii','ignore')` - `dt.encode('ascii','decode')` and some others also, but none worked and same error msg generated.