Python implantation of sha256

sha256.py

def sha256(data):
    bytes = ""

    h0 = 0x6a09e667
    h1 = 0xbb67ae85
    h2 = 0x3c6ef372
    h3 = 0xa54ff53a
    h4 = 0x510e527f
    h5 = 0x9b05688c
    h6 = 0x1f83d9ab
    h7 = 0x5be0cd19
    
    k = 64*[0]
    
    k =[
        0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
        0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
        0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
        0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
        0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
        0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
        0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
        0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2]
    
    def ror(x, y):
        return ((x >> y) | (x << (32-y))) & 0xFFFFFFFF

    for n in range(len(data)):
        bytes+='{0:08b}'.format(ord(data[n]))
    bits = bytes+"1"
    pBits = bits
    #pad until length equals 448 mod 512
    while len(pBits)%512 != 448:
        pBits+="0"
    #append the original length
    pBits+='{0:064b}'.format(len(bits)-1)

    def chunks(l, n):
        return [l[i:i+n] for i in range(0, len(l), n)]
        
    def rol(n, b):
        return ((n << b) | (n >> (32 - b))) & 0xffffffff 
        
    for c in chunks(pBits, 512):
        words = chunks(c, 32)
        w = [0]*64
        for n in range(0, 16):
            w[n] = int(words[n], 2)
        for i in range(16, 64):
             s0 = ror(w[i-15], 7) ^ ror(w[i-15], 18) ^ (w[i-15] >> 3)
             s1 = ror(w[i-2], 17) ^ ror(w[i-2], 19) ^ (w[i-2] >> 10)
             w[i] = (w[i-16] + s0 + w[i-7] + s1) & 0xffffffff

        a = h0
        b = h1
        c = h2
        d = h3
        e = h4
        f = h5
        g = h6
        h = h7

        for i in range(0, 64):
            S1 = ror(e, 6) ^ ror(e, 11) ^ ror(e, 25)
            ch = (e & f) ^ ((~e) & g)
            temp1 = h + S1 + ch + k[i] + w[i]
            S0 = ror(a, 2) ^ ror(a, 13) ^ ror(a, 22)
            maj = (a & b) ^ (a & c) ^ (b & c)
            temp2 = S0 + maj
            
            h = g
            g = f
            f = e
            e = (d + temp1) & 0xffffffff
            d = c
            c = b
            b = a
            a = (temp1 + temp2) & 0xffffffff

        h0 = h0 + a & 0xffffffff
        h1 = h1 + b & 0xffffffff
        h2 = h2 + c & 0xffffffff
        h3 = h3 + d & 0xffffffff
        h4 = h4 + e & 0xffffffff
        h5 = h5 + f & 0xffffffff
        h6 = h6 + g & 0xffffffff
        h7 = h7 + h & 0xffffffff
            
    #b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9
    return '%08x%08x%08x%08x%08x%08x%08x%08x' % (h0, h1, h2, h3, h4, h5, h6, h7)

print sha256("hello world")