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Python xml - handle unclosed token

I am reading in hundreds of XML files and parsing them with xml.etree.ElementTree.
Quick background just fwiw:
These XML files were at one point totally valid but somehow when processing them historically my process which copied/pasted them may have corrupted them. (Turns out it was a flushing issue / with statement not closing, if you care, see the good help I got on that investigation at... Python shutil copyfile - missing last few lines ).
Anyway back to the point of this question.
I would still like to read in the first 100,000 lines or so of these documents which are valid XML. The files are only missing the last 4 or 5KB of a 6MB file. As alluded to earlier, though, the file just 'cuts out'. it looks like this:
</Maintag>
<Maintag>
<Change_type>NQ</Change_type>
<Name>Atlas</Name>
<Test>ATLS</Test>
<Other>NYSE</Other>
<Scheduled_E
where (perhaps obviously) Scheduled_E is the beginning of what should be another attribute, <.Scheduled_Event>, say. But the file gets cut short mid tag. Once again, before this point in the file, there are several thousand 'good' "Maintag" entries which I would like to read in, accepting the cutoff entry (and obviously anything that should have come after) as an unrecoverable fail.
A simple but incomplete method of dealing with this might be to simply - pre XML processing - look for the last instance of the string <./Maintag> in the file, and replace what follows (which will be broken, at some point) with the 'opening' tags. Again, this at least lets me process what is still there and valid.
If someone wants to help me out with that sort of string replacement, then fwiw the opening tags are:
<?xml version="1.0" encoding="ISO-8859-1" ?>
<FirstTag>
<Source FileName="myfile">
I am hoping that even easier than that, there might be an elementtree or beautifulsoup or other way of handling this situation... I've done a decent amount of searching and nothing seems easy/obvious.
Thanks

For dealing with unclosed elements -or token as in the title of this questioin-, I'd recommend to try lxml. lxml's XMLParser has recover option which documented as :
recover - try hard to parse through broken XML
For example, given a broken XML as follow :
from lxml import etree
xml = """
<root>
<Maintag>
<Change_type>NQ</Change_type>
<Name>Atlas</Name>
<Test>ATLS</Test>
<Other>NYSE</Other>
<Scheduled_E
"""
parser = etree.XMLParser(recover=True)
doc = etree.fromstring(xml, parser=parser)
print(etree.tostring(doc))
The recovered XML as printed by the above code is as follow :
<root>
<Maintag>
<Change_type>NQ</Change_type>
<Name>Atlas</Name>
<Test>ATLS</Test>
<Other>NYSE</Other>
<Scheduled_E/></Maintag></root>

Parse xbrl file in python

I am working on a xml parser.
The goal is to parse a number of different xml files where prefixes and tags remain consistent but namespaces change.
I am hence trying either:
to parse the xml just by <prefix:tags> without resolving (replacing) the prefix with the namespace. The prefixes remain unchanged from document to document.
to load automatically the namespaces so that the identifier (<prefix:tag>) could be replaced with the proper namespace.
just parse the xml by tag
I have tried with xml.etree.ElementTree.
I also had a look at lxml
I did not find any configuration option of the XMLParser in lxml that could help me out although here I could read an answer where the author suggests that lxml should be able to collect namespaces for me automatically.
Interestingly, parsed_file = etree.XML(file) fails with the error:
lxml.etree.XMLSyntaxError: Start tag expected, '<' not found, line 1, column 1
One example of the files I would like to parse is here

Do not care about ns prefixes, care about complete namespaces
Sometime, people do care about those short prefixes and forgetting, the are of secondary importance. They are only short reference to fully qualified namespace. E.g.
xmlns:trw="http://www.trw.com/20131231"
in xml means, from now on, the "trw:" stands for fully qualified namespace "http://www.trw.com/20131231". Note, that this prefix can be redefined to any other namespace in any following element and may get completely different meaning.
On the other hand, when you care about real meaning, what means here fully qualified namespace, you may think of "trw:row" as "{http://www.trw.com/20131231}row". This translated meaning will be reliable and will not change with prefix changes.
Parsing referred xml
The link to http://edgar.sec.gov/Archives/edgar/data/1267097/000104746914000925/trw-20131231.xml leads to an xml, which validates by xmlstarlet and which lxml is able to parse.
The error message you show is referring to very first character of the stream, so chances are you either met BOM byte in your file, or you are trying to read xml, which is gzipped and shall be decompressed first.
lxml and namespaces
lxml works with namespaces well. It allows you to use XPath expressions, which use namespaces. With controlling namspace prefix on output it is a bit more complex, as it is dependent on xmlns attributes, which are part of serialized document. If you want to modify the prefixes, you must somehow organize these xmlns attributes, often by moving all of the to the root element. At the same time, lxml keeps track of fully qualified namespace of each element, so at the moment of serialization, it will respect this full name as well as currently valid prefix for this namespace.
Handling these xmlna attributes is a bit of more code, refer to lxml documentation.

items = tree.xpath("*[local-name(.) = 'a_tag_goes_here']")
did the job. On top of that I had to browse the generated list items manually to define my other desired filtering functions.

Can not find declaration of element 'xml'

I'm getting a lot of parsing errors from python related to my xml file. I read elsewhere on stackoverflow that I should validate the xml file first.
I can't understand why this xml will not validate:
<xml><hive name="myprojectname">
XML validator says this
Error: Can not find declaration of element 'xml'.
Error Position: <xml><hive name="myprojectname">

This:
<xml><hive name="myprojectname">
doesn't validate in http://www.validome.org/xml/validate/, because first you have to check "Well-Formedness only" option there.
Second, it have to follow XML rules, http://en.wikipedia.org/wiki/XML#Well-formedness_and_error-handling. So this should look:
<xml><hive name="myprojectname"/></xml>

The validator you are using appears to be a DTD based validator. Unless you tell it to check for well formedness only (in which case it won't check if your elements and attributes are correct, just that you open/close elements in a sane order, quote your attribute values, etc) then you must start the XML document with a Doctype so that it can find the DTD.

Reading text from XML nodes using Python's libxml2

I am a first time XPath user and need to be able to get the text values of these different elements.. for instance time, title, etc.. I am using the libxml2 module in Python and so far have not had much luck getting just the values of the text I need. The code below here only returns the element tags.. i need the values.. any help would be GREATLY appreciated!
I'm using this code:
doc = libxml2.parseDoc(xmlOutput)
result = doc.xpathEval('//*')
With the following document:
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE SCAN_LIST_OUTPUT SYSTEM "https://qualysapi.qualys.com/api/2.0/fo/sca/scan_list_output.dtd">
<SCAN_LIST_OUTPUT>
<RESPONSE>
<DATETIME>2012-01-22T01:21:53Z</DATETIME>
<SCAN_LIST>
<SCAN>
<REF>scan/2343423</REF>
<TYPE>Scheduled</TYPE>
<TITLE><![CDATA[customer 1 5/20/2012]]></TITLE>
<USER_LOGIN>user1</USER_LOGIN>
<LAUNCH_DATETIME>2012-02-21T04:11:05Z</LAUNCH_DATETIME>
<STATUS>
<STATE>Finished</STATE>
</STATUS>
<TARGET><![CDATA[13.3.3.2, 13.8.8.10, 13.10.12.60, 13.10.12.11...]]></TARGET>
</SCAN>
</SCAN_LIST>
</RESPONSE>
</SCAN_LIST_OUTPUT>

You can call getContent() on each returned xmlNode object to retrieve the associated text. Note that this is recursive -- to non-recursively access text content in libxml2, you'll want to retrieve the associated text node under the element, and call .getContent() on that.
That said, this would be easier if you used lxml.etree (a higher-level Python API, still backing into the C libxml2 library) instead of the Python libxml2; in that case, it's simply element.text to access the associated content as a string.

Have a look at Mark Pilgrim's Dive Into Python 3, Chapter 12. XML
The chapter starts with short course to XML (general talk but with the Atom Syndication Feed example), then it continues with the standard xml.etree.ElementTree and continues with third party lxml that implements more with the same interface (full XPATH 1.0, based on libxml2).

Stripping (XML?) markup from a document using python

I've file which contains name of scientist in following format
<scientist_names>
<scientist>abc</scientist>
</scientist_names>
i want to use python to strip out name of scientists from above format How should I do it??
I would like to use regular epressions but don't know how to use it...please help

DO NOT USE REGULAR EXPRESSIONS! (all reasons well explained [here])
Use an xml/html parser, take a look at BeautifulSoup.

This is XML and you should use a XML parser like lxml instead of regular expressions (because XML is not a regular language).
Here is an example:
from lxml import etree
text = """<scientist_names> <scientist>abc</scientist> </scientist_names>"""
tree = etree.fromstring(text)
for scientist in tree.xpath("//scientist"):
print scientist.text

As noted, this appears to be xml. In that case, you should use an xml parser to parse this document; I recommend lxml ( http://lxml.de ).
Given your requirements, you may find it more convenient to use SAX-style parsing, rather than DOM-style, because SAX parsing simply involves registering handlers when the parser encounters a particular tag, as long as the meaning of a tag is not dependent on context, and you have more than one type of tag to process (which may not be the case here).
In case your input document may be incorrectly formed, you may wish to use Beautiful Soup: http://www.crummy.com/software/BeautifulSoup/bs3/documentation.html#Parsing XML

Here is an simple example that should handle the xml tags for you
#import library to do http requests:
import urllib2
#import easy to use xml parser called minidom:
from xml.dom.minidom import parseString
#all these imports are standard on most modern python implementations
#download the file if it's not on the same machine otherwise just use a path:
file = urllib2.urlopen('http://www.somedomain.com/somexmlfile.xml')
#convert to string:
data = file.read()
#close file because we dont need it anymore:
file.close()
#parse the xml you downloaded
dom = parseString(data)
#retrieve the first xml tag (<tag>data</tag>) that the parser finds with name tagName,
#in your case <scientist>:
xmlTag = dom.getElementsByTagName('scientist')[0].toxml()
#strip off the tag (<tag>data</tag> ---> data):
xmlData=xmlTag.replace('<scientist>','').replace('</scientist>','')
#print out the xml tag and data in this format: <tag>data</tag>
print xmlTag
#just print the data
print xmlData
If you find anything unclear just let me know