The use of whitespace indentation here doesn't match the tab indentation used everywhere else in this file. I think we should be consistent and stick to one method of indentation.

If you think it's worth going for whitespace indentation instead of \t, then I suggest creating a separate issue to change all uses of \t into whitespace.

err, are you sure about this? i dont see any tab (as it's supposed to be for every good python code) so i'm not sure what's going on here

I was referring to other lines in this file, like f.write('\t\ttitle: "%s",\n' % title) in function write_marker() above. That line has explicit \t characters that we write to the HTML file, while in write_infowindows() you've added the indentation as actual spaces.

Missing title parameter.

i'm gonna go thru your comments and fix them, just note all the changes are part of a working solution, which i've used in the past to create several maps; they are years old so i'm sure they need updating :)

i'll probably submit an additional commit for the fixes, as rebasing each commit with the fix is gonna be trouble, given all commits are built on top of each other so i'll have to go thru a list of infinite conflicts and merges. If you prefer, i can produce individual PRs for each change (but they will be 1st PR, gets approved and merge, 2nd PR, etc etc)

I think separating the PRs makes more sense; it'll keep the reviews shorter, but I really don't mind whatever approach you go for (all in one or separate PRs).

%s needs to be in quotes: '%s'

Let's also rename all mentions of point and self.points to marker and self.markers.

The default value should be [], not {}, since icons should always represent a list.

The same applies to settings.get('icons', {}) below.

Another write_symbols() function already exists in this file; can we extend that function instead of creating a new one here?

(This also means that we call self.write_symbols(f) twice above.)

The second %s needs quotes around it, otherwise any properties that are actually strings will end up as the following in the HTML file:

var goldStar = {
    scale: 1,
    strokeWeight: 14,
    fillColor: yellow, // (error)
    path: M 125,5 155,90 245,90 175,145 200,230 125,180 50,230 75,145 5,90 95,90 z, // (error)
    strokeColor: gold, // (error)
    fillOpacity: 0.8,
};

Similar to my write_symbols() comment below, there already exists an _add_symbol() function; can we also extend that instead of creating a new add_symbol() function?

Same goes for the already-existing self.symbols variable and the new self._symbols variable added here.

Is this correct? If icons is the following...

icons=[
      {
        'icon': 'symbolOne',
        'offset': '0%'
      }, {
        'icon': 'symbolTwo',
        'offset': '50%'
      }, {
        'icon': 'symbolThree',
        'offset': '100%'
      }
    ]

...then k will be the first dict object (not the first key of the first dict object).

It looks like you'll need two loops here, something like:

for icon in _icons:
    # (add `{` to `icons` string)
    for property in icon:
        # (add formatted `property` to `icons` string)
    # (add `}` to `icons` string)

Don't forget to remove the braces ({ and }) from f.write('icons: [{%s}],\n' % icons) below; we've added them in the above for-loop.

I think this is flipped; the first value should be the SW point, while the second should be the NE point, as per Google Maps.