Day 6 of Python (Dictionary, Set and Hashing)

Source: Dev.to

Dictionary

It is a collection used to store data in key:value pairs and it is a built-in data type, mutable and ordered.

id = {
    "name": "Vidya",
    "age": 21,
    "location": "Chennai",
    "gender": "Female"
}
print(id)

Output

{'name': 'Vidya', 'age': 21, 'location': 'Chennai', 'gender': 'Female'}

Set

It is a collection of items which is unordered, does not allow duplicate values and is mutable.

num = [1, 1, 2, 2, 2, 3, 3, 5, 5, 5]
freq = {}

for i in num:
    if i in freq:
        freq[i] = freq[i] + 1
    else:
        freq[i] = 1
print(freq)

Output

{1: 2, 2: 3, 3: 2, 5: 1}

Hashing

It is a technique that takes a key and converts it into a fixed integer value (hash value). This hash value is used to decide where to store and quickly retrieve data in memory.

print(hash("Vidya"))

Output

45823984723984

Hash collision

Sometimes two different keys produce the same hash, which causes a collision. Common strategies to handle collisions include open addressing and probing.