How to compute hashes:

frompyrollinghash.cyclichashimportCyclicHash# Initialize elementsread="CACTACACTAC"n=len(read)k=5ch=CyclicHash(k,64,1,1)# Hash the initial 5-gram with Hasher.eat()foriinrange(k):ch.eat(ord(read[i]))print(read[0:k],ch.hashvalue)# Hash the remainder 5-grams with Hasher.update(out, in)foriinrange(k,n):ngram=read[i-k+1:i+1]ch.update(ord(read[i-k]),ord(read[i]))print(ngram,ch.hashvalue)

CACTA 5677400150441078107ACTAC 18253274918174107859CTACA 13733297960976284091TACAC 2154973599019565330ACACT 9619269492940898979CACTA 5677400150441078107  # The pattern repeats againACTAC 18253274918174107859

Available hashers

Adler32

>>>frompyrollinghashimportAdler32>>>hasher=Adler32(3)# Set window size to 3>>>hasher.hashvalue# The hasher is reset0>>>foriinrange(3):# Hash 0, 1 ,2hasher.eat(i)>>>hasher.hashvalue458756>>>hasher.update(0,3)# Remove 0, add 3>>>hasher.hashvalue851975>>>hasher.reset()>>>hasher.hashvalue0>>>foriinrange(1,4):# Same result?hasher.eat(i)>>>hasher.hashvalue851975

CyclicHash

>>>frompyrollinghashimportCyclicHash>>>hasher=CyclicHash(3,64,1,1)>>>hasher.hashvalue0>>>foriinrange(3):# Hash 0, 1 ,2hasher.eat(i)>>>hasher.hashvalue17145202471131414222>>>hasher.update(0,3)# Remove 0, add 3>>>hasher.hashvalue7164181364666550526>>>hasher.reset()>>>hasher.hashvalue0>>>foriinrange(1,4):# Check that we will get the same hash with 1-3hasher.eat(i)>>>hasher.hashvalue7164181364666550526

GeneralHash

>>>frompyrollinghashimportGeneralHash>>>hasher=GeneralHash(3,19)>>>hasher.hashvalue0>>>foriinrange(3):# Hash 0, 1 ,2hasher.eat(i)>>>hasher.hashvalue434959>>>hasher.update(0,3)# Remove 0, add 3>>>hasher.hashvalue7153>>>hasher.reset()>>>hasher.hashvalue0>>>foriinrange(1,4):# Check that we will get the same hash with 1-3hasher.eat(i)>>>hasher.hashvalue7153

ThreeWiseHash

>>>frompyrollinghashimportThreeWiseHash>>>hasher=ThreeWiseHash(3,64)>>>hasher.hashvalue# Not 0. Doesn't matter.140542657667792>>>foriinrange(3):# Hash 0, 1 ,2hasher.eat(i)>>>hasher.hashvalue9309819415051597224>>>hasher.update(0,3)# Remove 0, add 3>>>hasher.hashvalue4181938747326092072>>>hasher.reset()>>>hasher.hashvalue0>>>foriinrange(1,4):# Check that we will get the same hash with 1-3hasher.eat(i)>>>hasher.hashvalue4181938747326092072

RabinKarpHash

>>>frompyrollinghashimportKarpRabinHash>>>hasher=KarpRabinHash(3,64)>>>hasher.hashvalue0>>>foriinrange(3):# Hash 0, 1 ,2hasher.eat(i)>>>hasher.hashvalue5277449530275385433>>>hasher.update(0,3)# Remove 0, add 3>>>hasher.hashvalue13252376563992438057>>>hasher.reset()>>>hasher.hashvalue0>>>foriinrange(1,4):# Check that we will get the same hash with 1-3hasher.eat(i)>>>hasher.hashvalue13252376563992438057

References