Question

I am trying to extract all occurrences of tagged words from a string using regex in Python 2.7.2. Or simply, I want to extract every piece of text inside the [p][/p] tags.
Here is my attempt:

regex = ur"[\u005B1P\u005D.+?\u005B\u002FP\u005D]+?"
line = "President [P] Barack Obama [/P] met Microsoft founder [P] Bill Gates [/P], yesterday."
person = re.findall(pattern, line)

Printing person produces ['President [P]', '[/P]', '[P] Bill Gates [/P]']

What is the correct regex to get: ['[P] Barack Obama [/P]', '[P] Bill Gates [/p]']
or ['Barrack Obama', 'Bill Gates'].

Answer 1

import re
regex = ur"\[P\] (.+?) \[/P\]+?"
line = "President [P] Barack Obama [/P] met Microsoft founder [P] Bill Gates [/P], yesterday."
person = re.findall(regex, line)
print(person)

yields

['Barack Obama', 'Bill Gates']

---

The regex ur"[\u005B1P\u005D.+?\u005B\u002FP\u005D]+?" is exactly the same
unicode as u'[[1P].+?[/P]]+?' except harder to read.

The first bracketed group [[1P] tells re that any of the characters in the list ['[', '1', 'P'] should match, and similarly with the second bracketed group [/P]].That’s not what you want at all. So,

• Remove the outer enclosing square brackets. (Also remove the
  stray 1 in front of P.)
• To protect the literal brackets in [P], escape the brackets with a
  backslash: \[P\].
• To return only the words inside the tags, place grouping parentheses
  around .+?.