Is there a way to filter a django queryset based on string similarity (a la python difflib)?

I have a need to match cold leads against a database of our clients.

The leads come from a third party provider in bulk (thousands of records) and sales is asking us to (in their words) "filter out our clients" so they don't try to sell our service to a established client.

Obviously, there are misspellings in the leads. Charles becomes Charlie, Joseph becomes Joe, etc. So I can't really just do a filter comparing lead_first_name to client_first_name, etc.

I need to use some sort of string similarity mechanism.

Right now I'm using the lovely difflib to compare the leads' first and last names to a list generated with Client.objects.all(). It works, but because of the number of clients it tends to be slow.

I know that most sql databases have soundex and difference functions. See my test of it in the update below - it doesn't work as well as difflib.

Is there another solution? Is there a better solution?

Edit:

Soundex, at least in my db, doesn't behave as well as difflib.

Here is a simple test - look for "Joe Lopes" in a table containing "Joseph Lopes":

with temp (first_name, last_name) as (
select 'Joseph', 'Lopes'
union
select 'Joe', 'Satriani'
union
select 'CZ', 'Lopes'
union
select 'Blah', 'Lopes'
union
select 'Antonio', 'Lopes'
union
select 'Carlos', 'Lopes'
)
select first_name, last_name
  from temp
 where difference(first_name+' '+last_name, 'Joe Lopes') >= 3
 order by difference(first_name+' '+last_name, 'Joe Lopes')

The above returns "Joe Satriani" as the only match. Even reducing the similarity threshold to 2 doesn't return "Joseph Lopes" as a potential match.

But difflib does a much better job:

difflib.get_close_matc