Helps to recognize a celular phone number in a string with non-celular numbers.

regognize_phone.py

#-*- coding: UTF-8 -*-

import re


def recognize_phone(s):
    """
    >>> f = recognize_phone
    >>> f(u'8-912-234-56-78')
    u'8-912-234-56-78'
    
    >>> f(u'8-912-234-56-78 факс:8-343-234-56-78')
    u'8-912-234-56-78'
    >>> f(u'тел. 8-912-234-56-78 8-343-234-56-78')
    u'8-912-234-56-78'
    >>> f(u'8-343-234-56-78 8-912-234-56-78')
    u'8-912-234-56-78'
    >>> f(u' тел. 8-343-234-56-78 тел. 8-912-234-56-78 ')
    u'8-912-234-56-78'
    >>> f(u'(29)36-41-34; 8-912-234-56-78')
    u'8-912-234-56-78'
    >>> f(u'8/912/234-56-78')
    u'8/912/234-56-78'
    """
    
    m = re.search(r'\b(\+?[87][/\-]9[0-9/\-]+)', s)
    if m:
        return m.group(0)

For other side - in my project i force user to input phone number as solid number string w/o spaces, minus or other marks and then parce rhem from end (in case if number not in international format)

def phone(num):
    """
    Phone formatter.
    """
    num = re.sub('\D', '', num)

    return '+%s (%s) %s-%s-%s' % (
        num[:-10],
        num[-10:-7],
        num[-7:-4],
        num[-4:-2],
        num[-2:]
    )