python not free memory ?

python_not_free_mem.py

#!/usr/bin/python3

import os
import uuid
import psutil

RELEASE_MEMORY = True

def get_rss_memory():
    p = psutil.Process(pid=os.getpid())
    with p.oneshot():
        return p.memory_full_info().rss / 1024 / 1024

l1 = []

for _ in range(1000000):
    record = {
        'key1': str(uuid.uuid4()),
        'key2': str(uuid.uuid4()),
        'key3': str(uuid.uuid4()),
        'key4': str(uuid.uuid4()),
        'key5': str(uuid.uuid4()),
    }
    l1.append(record)

print("%d Mb" % get_rss_memory())

l2 = []
for record in l1:
    new_record = {}

    if RELEASE_MEMORY:
        new_record['key1'] = (record['key1'] + '.')[:-1]
    else:
        new_record['key1'] = record['key1']

    l2.append(new_record)

print("%d Mb" % get_rss_memory())

l1 = l2

if RELEASE_MEMORY:
    print("%d Mb <- all ok, it has to be about 350Mb ???" % get_rss_memory())
else:
    print("%d Mb <- what is hell here it has to be about 350Mb ???" % get_rss_memory())