>>> selected_mako_conditionals = []

    >>> mako_variable_values = {'mako_variable': 'VALUE', 'mako_function': (lambda: 'FUNCTION RESULT'),

    ...                         'conditional_options': 'option-a'}

    >>> settings = { # only partially used

    ...     '[first-section]': {'variable2': 'VAL2', 'first_extra': 'EXTRA'},

    ...     '[third-section]': {'third_extra': ' 3'},

    ...     '[fourth-section]': {'fourth_extra': '4', 'fourth': '"four"'},

    ... }

    >>> print expand(template, mako_variable_values, settings)

    <BLANKLINE>

    [first-section]

    <BLANKLINE>

    variable=VALUE

    #variable2  =    value after tab

    variable2 = VAL2

    <BLANKLINE>

    first_extra = EXTRA

    <BLANKLINE>

    <BLANKLINE>

    # FUNCTION RESULT

    [second-section]

    # option a was chosen

    <BLANKLINE>

    [fourth-section]

    fourth = "four"

    fourth_extra = 4

    <BLANKLINE>

    [third-section]

    third_extra =  3

    <BLANKLINE>

    """

    mako_variables = dict(default_variables)

    mako_variables.update(mako_variable_values or {})

    settings = dict((k, dict(v)) for k, v in settings.items()) # deep copy before mutating

    ini_lines = mako.template.Template(template).render(**mako_variables)

    def process_section(m):

        """process a ini section, replacing values as necessary"""

        sectionname, lines = m.groups()

        if sectionname in settings:

            section_settings = settings.pop(sectionname)

            def process_line(m):

                """process a section line and update value if necessary"""

                key, value = m.groups()

                line = m.group(0)

                if key in section_settings:

                    # keep old entry as example - comments might refer to it

                return line.rstrip()

            # process lines that not are comments or empty and look like name=value

            lines = re.sub(r'^([^#\n\s]*)[ \t]*=[ \t]*(.*)$', process_line, lines, flags=re.MULTILINE)

            # add unused section settings

            if section_settings:

                lines += '\n' + ''.join('%s = %s\n' % (key, value) for key, value in sorted(section_settings.items()))

        return sectionname + '\n' + lines

    # process sections until comments before next section or end

    ini_lines = re.sub(r'''^

        (\[.*\])\n

        # after the section name, a number of chunks with:

        (

            (?:

                # a number of comments or empty lines

                (?:[#].*\n|\n)*

                # one or more non-empty non-comments non-section-start lines

                (?:[^\n#[].*\n)+

                # a number of comments - not empty lines

                (?:[#].*\n)*

            )*

        )

        ''',

        process_section, ini_lines, flags=re.MULTILINE|re.VERBOSE) \

        + \

        ''.join(

            '\n' + sectionname + '\n' + ''.join('%s = %s\n' % (key, value) for key, value in sorted(section_settings.items()))

            for sectionname, section_settings in sorted(settings.items())

            if section_settings)

    return ini_lines

def create(dest_file, mako_variable_values, settings):

    """Create an ini file at dest_file"""

    with open(template_file, 'rb') as f:

        template = f.read().decode('utf-8')

    ini_lines = expand(template, mako_variable_values, settings)

    with open(dest_file, 'wb') as f:

        f.write(ini_lines.encode('utf-8'))