import re
from string import digits

PHONE_RE = re.compile('([(]{0,1}[2-9]d{2}[)]{0,1}[-_. ]{0,1}[2-9]d{2}[-_. ]{0,1}d{4})')

def numbers2links(s):
    result = ""
    last_match_index = 0
    for match in PHONE_RE.finditer(s):
          raw_number = match.group()
          number = ''.join(d for d in raw_number if d in digits)
          call = '<a href="tel:%s">%s</a>' % (number, raw_number)
          result += s[last_match_index:match.start()] + call
          last_match_index = match.end()
    result += s[last_match_index:]
    return result

>>> numbers2links("Ghost Busters at (555) 423-2368! How about this one: 555 456 7890! 555-456-7893 is where its at.")
'Ghost Busters at <a href="tel:5554232368">(555) 423-2368</a>! How about this one: <a href="tel:5554567890">555 456 7890</a>! <a href="tel:5554567893">555-456-7893</a> is where its at.'
	
import re

PHONE_RE = re.compile('([(]{0,1}[2-9]d{2}[)]{0,1}[-_. ]{0,1}[2-9]d{2}[-_.  ]{0,1}d{4})')
NON_NUMERIC = re.compile('D')

def numbers2links(s):

   def makelink(mo):
      raw_number = mo.group()
      number = NON_NUMERIC.sub("", raw_number)
      return '<a href="tel:%s">%s</a>' % (number, raw_number)

   return PHONE_RE.sub(makelink, s)


print numbers2links("Ghost Busters at (555) 423-2368! How about this one: 555 456 7890! 555-456-7893 is where its at.")
	
((00|+)?1[. -]?)?(?[2-9][0-8][0-9])?[. -]?[2-9](00|[2-9]{2})[. -]?(?!0{4})d{4}([. -]?[x#-]d+)?
| A       |S   |  |   B                | S   |   C             | S  |  D           | S  |  E      |