Python Regex Google App Engine

>>> import re

>>> s = '<TD><FONT FACE="Arial,helvetica" SIZE="-2">V1068078</FONT></TD>'

>>> a = re.search(r'(.*)(V[0-9]{7,})',s)

>>> a.group(2)
'V1068078'

EDIT

(.*) is a greedy method. re.search(r'V[0-9]{7,}',s) will do the extraction with out greed.

EDIT as @Kaneg said, you can use findall for all instances. You will get a list with all occurrences of 'V[0-9]{7,}'

How can I do this in the XPath?

You can use starts-with() here.

>>> from lxml import etree
>>> html = '<TD><FONT FACE="Arial,helvetica" SIZE="-2">V1068078</FONT></TD>'
>>> tree = etree.fromstring(html)
>>> mls  = tree.xpath("//TD/FONT[starts-with(text(),'V')]")[0].text
'V1068078'

Or you can use a regular expression

>>> from lxml import etree
>>> html = '<TD><FONT FACE="Arial,helvetica" SIZE="-2">V1068078</FONT></TD>'
>>> tree = etree.fromstring(html)
>>> mls  = tree.xpath("//TD/FONT[re:match(text(), 'V\d{7,}')]", 
           namespaces={'re': 'http://exslt.org/regular-expressions'})[0].text
'V1068078'

Below example can match multiple cases:

import re
s = '<TD><FONT FACE="Arial,helvetica" SIZE="-2">V10683333</FONT></TD>,' \
' <TD><FONT FACE="Arial,helvetica" SIZE="-2">V1068333333</FONT></TD>'
m = re.findall(r'V\d{7,}', s)
print m

The following will work:

result = re.search(r'V\d{7,}',s)
print result.group(0)  # prints 'V1068078'

It will match any string of numeric digit of length 7 or more that follows the letter V

EDIT

If you want it to find all instances, replace search with findall

s = '<TD><FONT FACE="Arial,helvetica" SIZE="-2">V1068078</FONT></TD>V1068078   V1068078   V1068078'
re.search(r'V\d{7,}',s)
['V1068078', 'V1068078', 'V1068078', 'V1068078']

For everyone that keeps posting purely regex solutions, you need to read the question -- the problem is not just formulating a regular expression; it is an issue of isolating the right nodes of the XML/HTML document tree, upon which regex can be employed to subsequently isolate the desired strings.

You didn't show any of your import statements -- are you trying to use ElementTree? In order to use ElementTree you need to have some understanding of the structure of your XML/HTML, from the root down to the target tag (in your case, "TD/FONT"). Next you would use the ElementTree methods, "find" and "findall" to traverse the tree and get to your desired tags/attributes.

As has been noted previously, "ElementTree uses its own path syntax, which is more or less a subset of xpath. If you want an ElementTree compatible library with full xpath support, try lxml." ElementTree does have support for xpath, but not the way you are using it here.

If you indeed do want to use ElementTree, you should provide an example of the html you are trying to parse so everybody has a notion of the structure. In the absence of such an example, a made up example would look like the following:

import xml, urllib2
from xml.etree import ElementTree


url = "http://www.uniprot.org/uniprot/P04637.xml"
response = urllib2.urlopen(url)
html = response.read()
tree = xml.etree.ElementTree.fromstring(html)
# namespace prefix, see https://stackoverflow.com/questions/1249876/alter-namespace-prefixing-with-elementtree-in-python
ns = '{http://uniprot.org/uniprot}'
root = tree.getiterator(ns+'uniprot')[0]
taxa = root.find(ns+'entry').find(ns+'organism').find(ns+'lineage').findall(ns+'taxon')
for taxon in taxa:
  print taxon.text

# Output:
Eukaryota
Metazoa
Chordata
Craniata
Vertebrata
Euteleostomi
Mammalia
Eutheria
Euarchontoglires
Primates
Haplorrhini
Catarrhini
Hominidae
Homo

And the one without capturing groups.

>>> import re
>>> str = '<TD><FONT FACE="Arial,helvetica" SIZE="-2">V1068078</FONT></TD>'
>>> m = re.search(r'(?<=>)V\d{7}', str)
>>> print m.group(0)
V1068078