Python XML parsing, extraction and renaming files

Some style changes can happen, most are described here.

• Using single letter variable names can be hard to understand, and don't explain what the data is well. It is good not to use them.
• str.format is the best way to put variables into strings. E.G. '{}_{}.cps'.format(xmlfile, name_suffix)
• CONSTANTS should be all caps. MODEL_FILE = 'ct.cps'
• When passing 'kwargs' don't put spaces around the = operator. E.G. encoding='utf-8'
• Use new-lines sparingly.
• In-line comments are harder to read then comments before the code.
• Comments should have a space between the '#' and the comment.

It may be good to change create_paramsuffix_copies to a generator, in this case it should be faster than making a list.

def create_paramsuffix_copies(xmlfile):
    NSMAP = {"c": "http://www.copasi.org/static/schema"}
    parsed = ET.parse(xmlfile)
    for a in parsed.xpath("//c:Reaction", namespaces=NSMAP):
        for b in a.xpath(".//c:Constant", namespaces=NSMAP):
            yield '{}_{}'.format(a.attrib['name'], b.attrib['name'])

You could add docstrings to your program so people know what the functions do at a later date.

But it looks really good!