5.1.10 - HashMap (Dictionary)

mymap = {}
mymap["alice"] = 88
len(mymap) # 1, number of keys in the hashmap
 
# we can also modify the value of the key
mymap['alice'] = 10
 
# We can also search for a key in a hashmap in constant time
print("alice" in mymap) # True
 
mymap.pop("alice")
 
mymap = { "alice": 90, "bob": 70 }

Dict comprehension

Useful for graph problems and building adjacency list

mymap = { i: 2*i for i in range(3) }

i is the key and the value is 2*i

Looping through a hashmap

mymap = { "alice": 90, "bob": 70 }
for key in mymap:
    print(key, mymap[key])
    
for val in mymap.values():
    print(val)
 
for key, val, in mymap.items():
    print(key, val)