如何释放python的内存

python小白一枚，为了练习在jupyter lab搞了很多数据练习，但是现在一跑程序内存就减少，最后就连页面都打不开，有什么办法可以释放内存吗？网上看了说要删除变量，但是一堆ipynb文件实在没办法一个个删除啊，求助！！

>>> from pympler import tracker
>>> import random
>>> tr = tracker.SummaryTracker()
>>> a = [[random.random() for i in range(2000)] for i in range(2000)]
>>> tr.print_diff()
                                                     types |   # objects |   total size
========================================================== | =========== | ============
                                                     float |     4000000 |     91.55 MB
                                                      list |        4286 |     31.82 MB
                                                       str |        2035 |    109.42 KB
                                                      dict |          86 |     87.34 KB
                                                       int |         233 |      5.46 KB
  <class 'pyreadline.lineeditor.lineobj.ReadLineTextBuffer |          84 |      4.59 KB
                                        wrapper_descriptor |           9 |    648     B
                                                   unicode |           5 |    260     B
                                         getset_descriptor |           4 |    256     B
                                         member_descriptor |           3 |    192     B
                                                   weakref |           2 |    160     B
                                                      code |           1 |    128     B
                                     function (store_info) |           1 |    112     B
                                                      cell |           2 |     96     B
                                                     tuple |           0 |      8     B
>>> import gc
>>> gc.collect()
0
>>> from sys import getsizeof
>>> getsizeof(a)
16560