def strip_comments(s):
    """Strips the comments from a multi-line string.
    
    >>> strip_comments('hello ;comment\\nworld')
    'hello \\nworld'
    """
    COMMENT_CHAR = ';'
    lines = []
    for line in s.split('\n'):
        if COMMENT_CHAR in line:
            lines.append(line[:line.index(COMMENT_CHAR)])
        else:
            lines.append(line)
    return '\n'.join(lines)