dict features:
(1) The speed of searching and inserting is fast, and will not slow down as the key increases.
(2) It takes up a lot of memory
list features:
(1) The time of searching and inserting will increase with the increase of elements.
(2) Small footprint and less wasted memory.
Summary: Dictionaries use space in exchange for time, and the keys of dict must be immutable objects.
Dictionaries and lists are mutable sequences.