For loop inside for loop

[vbx_wx]

Hello,how can I make the 2 for`s to work at the same time to find out the diferences between A and B ? Thank you.

A = "gtggcaacgtgc"
B = "gtagcagcgcgc"
C = "gcggcacagggt"
D = "gtgacaacgtgc"

def cromo(a, b):
    inc = 0
    for i in a:
        for j in b:
            if i != j:
                inc = inc + 1;
    print inc
    
cromo(A, B)

[Gribouillis]

You can use this

# python 2
A = "gtggcaacgtgc"
B = "gtagcagcgcgc"
C = "gcggcacagggt"
D = "gtgacaacgtgc"

def cromo(a, b):
    assert len(a) == len(b)
    return sum(a[i] != b[i] for i in xrange(len(a)))
    
print cromo(A, B)

Boolean values can be summed, with True=1 and False=0.

[woooee]

Only one for loop would be used because you want to access the same relative position in each string. Also, do not use "i" as a variable name as it looks too much like the number 1.

def cromo(a, b):
    inc = 0
    if len(a) != len(b):
        print "both strings must be the same length"
        return -1

    for ctr in range(len(a)):
        if a[ctr] != b[ctr]:
            inc = inc + 1
    print inc
    return inc
 
A = "gtggcaacgtgc"
B = "gtagcagcgcgc"
print cromo(A, B)