Question

list1 = ['Contact: Hamdan Z Hamdan, MBBS, Msc',
        '\r\n            ',
        '[phone]',
        '\r\n                  ',
        '[e-mail]',
        '\r\n                ',
        'Contact: Maha I Mohammed, MBBS, PhD',
        '\r\n            ',
        '[phone]',
        '\r\n                  ',
        '\r\n                ',
        'Sudan',
        'Jaber abo aliz',
        '\r\n                  ',
        'Recruiting',
        '\r\n          ',
        'Khartoum, Sudan, 1111  ',
        u'Contact: Khaled H Bakheet, MD,PhD \xa0 \xa0 [phone] \xa0 \xa0 ',
        '[e-mail]',
        u' \xa0 \xa0 ',
        u'Principal Investigator: Hamdan Z Hamdan, MBBS,MSc \xa0 \xa0  \xa0 \xa0  \xa0 \xa0 ',
       'Principal Investigator:',
       '\r\n      ',
       'Hamdan Z Hamdan, MBBS, MSc',
       '\r\n            ',
        'Al-Neelain University',
        '\r\n                '
    ]

From this list of strings I need to extract only 4 digit integers which should not be associated with other characters?

Example: ‘1111’ only is the needed output.

How we should write the regex in python? Obviously, this won’t work: *([\d]{4})*.

Answer 1

You can use \b in a regular expression to indicate a word boundary, so the following will work for you:

import re

for s in list1:
    m = re.search(r'\b\d{4}\b', s)
    if m:
        print m.group(0)

… which just outputs 1111. The documentation for \b explains further:

\b

Matches the empty string, but only at the beginning or end of a word. A word is defined as a sequence of alphanumeric or underscore characters, so the end of a word is indicated by whitespace or a non-alphanumeric, non-underscore character. […]