A Rust CrackMe Password Checksum Generator and a failed BruteForcer (it just takes too much time XD)

get_checksum.py

import binascii
import itertools
import sys

def add_hex(A, B):
    A = "0"+A
    B = "0"+B
    #Remember all pattern include carry in variable d.
    i2h = dict(zip(range(16), "0123456789abcdef"))
    a = [(i,j) for i in "0123456789abcdef" for j in "0123456789abcdef"]
    b = list(map(lambda t: int(t[0],16)+int(t[1],16), a))
    c = ["0"+i2h[i] if i<16 else "1"+i2h[i-16] for i in b]#list of digit include carry
    d = dict(zip(a,c))#d={(digit,digit):digit,,,}
    #Calculate with variable d.
    result = ""
    cur = "0"
    nex = "0"
    for i in itertools.zip_longest(A[::-1], B[::-1], fillvalue = "0"):
        cur = d[(nex, d[i][1])][1]                   #cur = carry + digit + digit
        if d[i][0]=='1' or d[(nex, d[i][1])][0]=='1':#nex = carry = carry + digit + digit
            nex = "1"
        else:
            nex = "0"
        result += cur

    return result[::-1]

def getChecksum(s):
    a = binascii.hexlify(bytes(s, encoding="utf8"))
    r = 0

    for i in range(0, len(a), 2):
        n = str(a[i:i+2].decode('utf-8'))
        r = add_hex(n, str(r))
    return r.strip('0')

def BruteForce():
    chars = "0123456789abcdefghijklmnopqrstuvwxyz"

    n = 3

    with open('bruteforce_log.txt', 'w') as fh:
        for i in range(1, n + 1):
            for item in itertools.product(chars, repeat=i):
                s = "".join(item)
                # print('checksum of: [','%s' % s, ']', 'is ', '%s' % getChecksum(s))
                fh.write(f'checksum for: [{s}] is [{getChecksum(s)}]\n')
    fh.close() 

BruteForce()
print('DONE!')
#print('0x{:X}'.format(int(getChecksum(str(sys.argv[1])), 16)))