Apply Set Operations on Redis Sets using Python and Redis-Py

Overview:

Redis supports several mathematical operations that are defined on sets, which include

Membership of an element in a set
Union of sets
Intersection sets
Subtraction of sets

Set Membership:

Any Set consists of one or more elements. A set without any member is called a null set.
The Redis command, SISMEMBER checks whether an element is a member of a set.

Example:

# Example Python program to demonstrate set membership operation in Redis

import redis

redisClient = redis.StrictRedis(host='localhost',

port=6379,

db=0)

# Define a set of prime numbers

redisClient.sadd("primes", 2, 3, 5, 7)

# Check if 6 is a prime number

print("Is 6 a prime number? {}".format(redisClient.sismember("primes", 8)))

# Check if 7 is a prime number

print("Is 7 a prime number? {}".format(redisClient.sismember("primes", 7)))

Output:

Is 6 a prime number? False

Is 7 a prime number? True

Set Union:

Union of 'n' sets is a set, which has elements that are part of either the individual sets or part of many of them.
The Redis command SUNION provides the Union of multiple sets.
The command SUNIONSTORE provided by Redis is similar to SUNION. However, SUNIONSTORE stores the resultant union of multiple sets in a destination set provided.

Example:

# Example Python program to demonstrate set union in Redis

import redis

redisClient = redis.StrictRedis(host='localhost',

port=6379,

db=0)

# Define multiple sets of fruits

redisClient.sadd("Fruits1", "Pear", "Peach", "Guava", "Melon")

redisClient.sadd("Fruits2", "Apple", "Melon", "Berry", "Mango")

redisClient.sadd("Fruits3", "Grapes", "Banana", "Melon", "Berry")

# Find the union of the redis sets

print(redisClient.sunion("Fruits1","Fruits2","Fruits3"))

# Define multiple sets of games

redisClient.sadd("Games1", "Cricket", "Hockey", "Base Ball")

redisClient.sadd("Games2", "Foot Ball", "Badminton", "Hockey")

redisClient.sadd("Games3", "Tennis", "Hockey", "Polo")

# Find the union of the redis sets and store it in the destination set provided

redisClient.sunionstore("Games4", "Games1","Games2","Games3")

# Print the members of the new set

print(redisClient.smembers("Games4"))

Output:

{b'Guava', b'Grapes', b'Pear', b'Peach', b'Apple', b'Melon', b'Berry', b'Banana', b'Mango'}

{b'Polo', b'Badminton', b'Base Ball', b'Hockey', b'Foot Ball', b'Tennis', b'Cricket'}

Set Intersection:

Intersection of multiple sets is provided by a set whose elements are present in all of those sets for which the Intersection is taken.
Redis has two commands to perform set intersection. One is SINTER and the other one is SINTERSTORE.
SINTER computes intersection of multiple sets and returns the resultant set.
SINTERSTORE is similar to SINTER. Instead of returning the intersection of multiple sets, SINTERSTORE stores it in the destination set provided.

Example:

# Example Python program to demonstrate set intersection in Redis

import redis

redisClient = redis.StrictRedis(host='localhost',

port=6379,

db=0)

# Define multiple sets of fruits in Redis

redisClient.sadd("FruitBasket1", "Pear", "Peach", "Guava", "Melon")

redisClient.sadd("FruitBasket2", "Apple", "Melon", "Berry", "Mango")

redisClient.sadd("FruitBasket3", "Grapes", "Banana", "Melon", "Berry")

# Find the intersection of multiple sets of fruits

newBasket = redisClient.sinter("FruitBasket1", "FruitBasket2", "FruitBasket3")

print("Intersection of fruit baskets:")

print(newBasket)

# Define multiple sets of games in Redis

redisClient.sadd("GameSet1", "Cricket", "Hockey", "Base Ball")

redisClient.sadd("GameSet2", "Foot Ball", "Badminton", "Hockey")

redisClient.sadd("GameSet3", "Tennis", "Hockey", "Polo")

# Find the intersection of multiple sets of games

redisClient.sinterstore("GameSetCommon","GameSet1", "GameSet2", "GameSet3")

print("Intersection of game sets:")

print(redisClient.smembers("GameSetCommon"))

Output:

Intersection of fruit baskets:

{b'Melon'}

Intersection of game sets:

{b'Hockey'}

Subtraction of sets:

Removing elements of A, which are also present in the other sets, provides the subtraction of multiple sets from a set A.
Redis provides SDIFF that computes and returns the difference set between the set A and all other sets.
The SDIFFSTORE command computes the difference set between the set A and all other sets. The difference set is stored in a destination set provided.

Example:

# Example Python program to demonstrate set difference operation in Redis

import redis

# Create a Redis client

redisClient = redis.StrictRedis(host='localhost',

port=6379,

db=0)

# Define multiple sets of numbers

redisClient.sadd("NumberSet1", 1, 2, 3, 4)

redisClient.sadd("NumberSet2", 2)

redisClient.sadd("NumberSet3", 3)

# Find the set difference between set 1 and all other sets

print(redisClient.sdiff("NumberSet1", "NumberSet2", "NumberSet3"))

# Define multiple sets of credit ratings

redisClient.sadd("CreditRatings1", "AAA", "AA", "BB")

redisClient.sadd("CreditRatings2", "BB")

redisClient.sadd("CreditRatings3", "AA")

# Find the set difference between CreditRatings set 1 and all other sets

# Store the results in CreditRatings4

redisClient.sdiffstore("CreditRatings4", "CreditRatings1", "CreditRatings2", "CreditRatings3")

print(redisClient.smembers("CreditRatings4"))

Output:

{b'4', b'1'}

{b'AAA'}