#!/usr/bin/python

import re

all_lines = '#hello\n#monica, how re "u?\n#hello#robert\necho'

regex = re.compile(
    r'''\#             # first hash
        .*             # continues to (note: .* greedy)
        \#             # last hash
        .*?$           # rest of the line. (note .*? non-greedy)
    ''',
    # Flags: 
    #   DOTALL: Make the '.' match any character at all, including a newline
    #   VERBOSE: Allow comments in pattern
    #   MULTILINE: Allow $ to match end of line
    re.DOTALL | re.VERBOSE | re.MULTILINE)

print re.search(regex, all_lines).group()