crc.py

def xor(a, b): 

    result = [] 
    for i in range(1, len(b)): 
        if a[i] == b[i]: result.append('0') 
        else: result.append('1') 

    return ''.join(result) 
   
def mod2div(divident, divisor): 

    pick = len(divisor) 
    tmp = divident[0 : pick] 

    while pick < len(divident): 
  
        if tmp[0] == '1': 
            tmp = xor(divisor, tmp) + divident[pick] 
  
        else:   
            tmp = xor('0'*pick, tmp) + divident[pick] 
 
        pick += 1
  
    if tmp[0] == '1': 
        tmp = xor(divisor, tmp) 
    else: 
        tmp = xor('0'*pick, tmp) 
  
    checkword = tmp 
    return checkword 
  
def encodeData(data, key): 
  
    l_key = len(key) 
    
    appended_data = data + '0'*(l_key-1) 
    remainder = mod2div(appended_data, key) 
 
    codeword = data + remainder 
    print("Remainder : ", remainder) 
    print("Encoded Data (Data + Remainder) : ", codeword) 
    return codeword
  
# Driver code 

data = input("Input Message sequence : ")
key = input("Input Generator Gpolynomial : ")

encoded_codeword = encodeData(data, key)

received = input("Received Message sequence : ")

if received == encoded_codeword:
    print("Received codeword is correct.")

else:
    print("Received codeword is wrong.")