Your question is not 100% clear, but I'm assuming you want to find every piece of text inside [P][/P]
tags:
>>> import re
>>> line = "President [P] Barack Obama [/P] met Microsoft founder [P] Bill Gates [/P], yesterday."
>>> re.findall('\[P\]\s?(.+?)\s?\[\/P\]', line)
['Barack Obama', 'Bill Gates']