String vs. List vs. Dictionary

String : 'hello'

- sequence of character

- immutable

error : s[i] = 'x'

- s[i] : i th character in s

List : ['alpha', 23]

- list of elements

- mutable

- p[i] : i th element of p

Dictionary : { 'hydrogen':1 , 'helium' : 23 }

- set of <key, value> pairs

- mutable

- d[k] : 

k : key

value associated with k in d