The encrypt method in my program is not encrypting correctly. I thought I figured out why using debug mode; it's because it reads the spaces between words as something it has to encrypt. So I tried typing a message without spaces but it still didn't come out correctly.
I figure the issue is the if statement with the key. I tried commenting lines out, changing statements, changing the if statement to a for loop, but it still isn't correct.
def main():
vig_square = create_vig_square()
message = input("Enter a multi-word message with punctuation: ")
input_key = input("Enter a single word key with no punctuation: ")
msg = message.lower()
key = input_key.lower()
coded_msg = encrypt(msg, key, vig_square)
print("The encoded message is: ",coded_msg)
print("The decoded message is: ", msg)
def encrypt(msg,key,vig_square):
coded_msg = ""
key_inc = 0
for i in range(len(msg)):
msg_char = msg[i]
if key_inc == len(key)-1:
key_inc = 0
key_char = key[key_inc]
if msg_char.isalpha() and key_char.isalpha():
row_index = get_row_index(key_char,vig_square)
col_index = get_col_index(msg_char,vig_square)
coded_msg = coded_msg+vig_square[row_index][col_index]
else:
coded_msg = coded_msg + " "
key_inc = key_inc+1
return coded_msg
def get_col_index(msg_char, vig_square):
column_index = ord(msg_char) - 97
return column_index
def get_row_index(key_char, vig_square):
row_index = ord(key_char) - 97
return row_index
def create_vig_square():
vig_square = list()
for row in range(26):
next_row = list()
chr_code = ord('a') + row
for col in range(26):
letter = chr(chr_code)
next_row.append(letter)
chr_code = chr_code + 1
if chr_code > 122:
chr_code = ord('a')
vig_square.append(next_row)
return vig_square
main()
This example was given to us:
Enter a multi-word message with punctuation: The eagle has landed.
Enter a single word key with no punctuation: LINKED
The encoded message is: epr oejwm ukw olvqoh.
The decoded message is: the eagle has landed.
But my encoded message comes out as:
epr iloyo sif plvqoh
You have two errors:
First, you don't use all characters in the key. Change the following line:
if key_inc == len(key)-1:
key_inc = 0
to
if key_inc == len(key):
key_inc = 0
Second, you move the key pointer even if you process a non-alpha character in the message (e.g. spaces). Do it only if you encode a character, i.e. make the following change:
if msg_char.isalpha() and key_char.isalpha():
...
key_inc = key_inc+1 # Move this line here
else:
...