Hamming Distance Between Two Strings In Python

Question

I'm new to Python and I need to find the Hamming distance between two strings:

chaine1 = 6fb17381822a6ca9b02153d031d5d3da

chaine2 = a242eace2c57f7a16e8e872ed2f2287d

The XOR function didn't work, and my search on the web was not very successful.

I tried to modify something I found on the web, but there's some invalid syntax...:

assert len (chaine1) == len(chaine2)

return sum(chaine1 != chaine2 for chaine1, chaine2 in zip(chaine1, chaine2))


if __name__=="__main__":    
chaine1 = hashlib.md5("chaine1".encode()).hexdigest()

chaine2 = hashlib.md5("chaine2".encode()).hexdigest()
print hamming_distance(chaine1, chaine2)

Any ideas on how I could proceed? Thanks!

Answer 1

Following is a program calculating hamming distance using two different ways.

import hashlib

def hamming_distance(chaine1, chaine2):
    return sum(c1 != c2 for c1, c2 in zip(chaine1, chaine2))

def hamming_distance2(chaine1, chaine2):
    return len(list(filter(lambda x : ord(x[0])^ord(x[1]), zip(chaine1, chaine2))))

if __name__=="__main__":    
    chaine1 = hashlib.md5("chaine1".encode()).hexdigest()
    chaine2 = hashlib.md5("chaine2".encode()).hexdigest()

    #chaine1 = "6fb17381822a6ca9b02153d031d5d3da"
    #chaine2 = "a242eace2c57f7a16e8e872ed2f2287d"

    assert len(chaine1) == len(chaine2)

    print(hamming_distance(chaine1, chaine2))

    print(hamming_distance2(chaine1, chaine2))

The reason why you get Invalid syntax: ... is probably you don't have any indentations, which are required in Python.

Answer 2

First should the definition of Hamming Distance between two string .

The hamming distance between two strings of equal length is the number of positions at which these strings vary. In more technical terms, it is a measure of the minimum number of changes required to turn one string into another.

Let's get a solution of it.

def hamming(s1,s2):
result=0
if len(s1)!=len(s2):
    print("String are not equal")
else:
    for x,(i,j) in enumerate(zip(s1,s2)):
        if i!=j:
            print(f'char not math{i,j}in {x}')
            result+=1
return result
s1="rover"
s2="river"
print(hamming(s1,s2))

Result: char not match ('o', 'i') in 1