does deepCopy copies the space left after delete from the old dictionary?

I am trying to delete keys from a dictionary according to Python reclaiming memory after deleting items in a dictionary . One solution proposed in the latter is:

to create a new dictionary by copying the old dictionary

In source code 1 I did the following:

I create a new dictionary new_flights
delete the key del flights[key]
finally use new_flights = copy.deepcopy(flights)

In source code 2 I did the following:

I create a new dictionary new_flights
copy to new dictionary new_flights[key] = flights[key]
finally flights.clear()

Both ways didn't work. The memory is not being freed.

Source code 1

 def remove_old_departure_dates(flights, search_date):
        new_flights = defaultdict(lambda : defaultdict(list))
        s_date = datetime.strptime(search_date,'%m/%d/%y')
        
        for key in flights.keys():
            dep_date = datetime.strptime(key.DDATE,'%m/%d/%y')
            if(s_date > dep_date):
                del flights[key]

        new_flights = copy.deepcopy(flights)
        flights.clear()
        return new_flights

Source code 2

def remove_old_departure_dates(flights, search_date):
    new_flights = defaultdict(lambda : defaultdict(list))
    s_date = datetime.strptime(search_date,'%m/%d/%y')
    
    for key in flights.keys():
        dep_date = datetime.strptime(key.DDATE,'%m/%d/%y')
        if(s_date > dep_date):
            new_flights[key] = flights[key]

    flights.clear()
    return new_flights

Source code after discussion

Based on the comments I did the following and used a deepcopy to remove the reference. Seems that it's working. Is that something correct?

def remove_old_departure_dates(flights, search_date):
    old_flights = defaultdict(lambda : defaultdict(list))
    new_flights = defaultdict(lambda : defaultdict(list))
    s_date = datetime.strptime(search_date,'%m/%d/%y')
    
    for key in flights.keys():
        dep_date = datetime.strptime(key.DDATE,'%m/%d/%y')
        if(s_date > dep_date):
            print "removing dates " + key.DDATE +" "+search_date
            old_flights[key] = copy.deepcopy(flights[key])
        else:
            new_flights[key] = copy.deepcopy(flights[key])

    return (old_flights, new_flights)

Asked by: Roland183 | Posted: 27-01-2022

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