Playfair.py

key = input("Enter key : ")
key = key.replace(" ", "")
key = key.upper()

def matrix(x, y, initial):
    return [[initial for i in range(x)] for j in range(y)]

result = list()
for c in key:
    if c not in result:
        if c == 'J':
            result.append('I')
        else:
            result.append(c)
flag = 0
for i in range(65, 91):
    if chr(i) not in result:
        if i == 73 and chr(74) not in result:
            result.append("I")
            flag = 1
        elif flag == 0 and i == 73 or i == 74:
            pass
        else:
            result.append(chr(i))
k = 0
my_matrix = matrix(5, 5, 0)
for i in range(0, 5):
    for j in range(0, 5):
        my_matrix[i][j] = result[k]
        k += 1


def locindex(c):
    loc = list()
    if c == 'J':
        c = 'I'
    for i, j in enumerate(my_matrix):
        for k, l in enumerate(j):
            if c == l:
                loc.append(i)
                loc.append(k)
                return loc


def encrypt():
    msg = str(input("ENTER MSG : "))
    msg = msg.upper()
    msg = msg.replace(" ", "")
    i = 0
    for s in range(0, len(msg) + 1, 2):
        if s < len(msg) - 1:
            if msg[s] == msg[s + 1]:
                msg = msg[:s + 1] + 'X' + msg[s + 1:]
    if len(msg) % 2 != 0:
        msg = msg[:] + 'X'
    print("CIPHER TEXT:", end=' ')
    while i < len(msg):
        loc = list()
        loc = locindex(msg[i])
        loc1 = list()
        loc1 = locindex(msg[i + 1])
        if loc[1] == loc1[1]:
            print("{}{}".format(my_matrix[(loc[0] + 1) % 5][loc[1]], my_matrix[(loc1[0] + 1) % 5][loc1[1]]), end=' ')
        elif loc[0] == loc1[0]:
            print("{}{}".format(my_matrix[loc[0]][(loc[1] + 1) % 5], my_matrix[loc1[0]][(loc1[1] + 1) % 5]), end=' ')
        else:
            print("{}{}".format(my_matrix[loc[0]][loc1[1]], my_matrix[loc1[0]][loc[1]]), end=' ')
        i = i + 2


def decrypt():
    msg = str(input("ENTER CIPHER TEXT:"))
    msg = msg.upper()
    msg = msg.replace(" ", "")
    print("PLAIN TEXT:", end=' ')
    i = 0
    while i < len(msg):
        loc = list()
        loc = locindex(msg[i])
        loc1 = list()
        loc1 = locindex(msg[i + 1])
        if loc[1] == loc1[1]:
            print("{}{}".format(my_matrix[(loc[0] - 1) % 5][loc[1]], my_matrix[(loc1[0] - 1) % 5][loc1[1]]), end=' ')
        elif loc[0] == loc1[0]:
            print("{}{}".format(my_matrix[loc[0]][(loc[1] - 1) % 5], my_matrix[loc1[0]][(loc1[1] - 1) % 5]), end=' ')
        else:
            print("{}{}".format(my_matrix[loc[0]][loc1[1]], my_matrix[loc1[0]][loc[1]]), end=' ')
        i = i + 2


while (1):
    choice = int(input("\n 1.Encryption \n 2.Decryption: \n 3.EXIT \n Enter Your Choice: \n "))

    if choice == 1:
        encrypt()
    elif choice == 2:
        decrypt()
    elif choice == 3:
        exit()
    else:
        print("Choose correct choice")