Python: Merging two dicts and setting the default values

Imagine you're browsing products in your local e-shop, there should be any filtering for their products. And once you select any filter the filters tab changes a bit, so if you have selected only products that have for example red colour, other options are gone. Let's say that you can only see red (53), 53 is the count of the products that are in the store. But what I'm trying to do in my store is to somehow also show the other options even if there are no products by that filter.

So I have two queries, first gets all the filters by this format:

First query returns all the available filters:

{'slugified_attrs.color': {'Red': 15}, 'slugified_attrs.size': {'XXL': 4, 'S': 45, 'M': 1, 'XS': 1}}

Second query returns only more available filters if there are any applied filters, in our case we have selected 'slugified_attrs.color': Red.

{'slugified_attrs.size': {'S': 2}}

We can see that this does not return options that have 0 counts, so we have to do it by ourself.

What I thought about is to first get all the available filters and then somehow check if second query does not have the filters. If the second query does not have that filter, for example {'XXL': 4, 'M': 1, 'XS': 1} update the second query with these filters, but change their counts to 0.

So it should look like:

{'slugified_attrs.color': {'Red': 15}, 'slugified_attrs.size': {'XXL': 0, 'S': 2, 'M': 0, 'XS': 0}}

But if the first query will have any matches with the second one, for example 'S': 45 and 'S': 2, we will have to override the S to be 2.

I've tried:

def merge_facets(self, target, second_query):
    first_query = target.copy()

    for key, filters_with_counts in first_query.items():

        for filter, count in filters_with_counts.items():
            if filter in second_query[key]:
                # Should update the local dict with new values?
                pass
            else:
                # Should insert new values with 0 counts?
                pass

source https://stackoverflow.com/questions/69351082/python-merging-two-dicts-and-setting-the-default-values