Requirements The # symbol denotes user input

$ python $3$

vigenere.py $-$e

Enter the key: "helloworld

Enter the plaintext: #The quick brown fox jumps over the lazy dog.

Ciphertext is: Alp bieqb muvay qct xlxsz sgpf pvv wdgc ozu.

$ python $3$

vigenere.py $-$d

Enter the key: "helloworld

Enter the ciphertext: #Alp bieqb muvay qct xlxsz sgpf pvv wdgc ozu.

Plaintext is: The quick brown fox jumps over the lazy dog.

Grouping

$ python $3$

vigenere.py $-$e $-$g $5$

Enter the key: "helloworld

Enter the plaintext: #The quick brown fox jumps over the lazy dog.

Ciphertext is: ALPBI EQBMU VAYQC TXLXS ZSGPF PVVWD GCOZU

$ python $3$

vigenere.py $-$d $-$g $5$

Enter the key: thelloworld

Enter the ciphertext: #Alp bieqb muvay qct xlxsz sgpf pvv wdgc ozu.

Plaintext is: THEQU ICKBR OWNFO XJUMP SOVER THELA ZYDOG

$ python $3$

vigenere.py $-$e $-$g $5$

Enter the key: "helloworld

Enter the plaintext: #The quick brown fox.

Ciphertext is: ALPBI EQBMU VAYQC T

In the third example, since we didn't have enough characters to make a full group, our last group

just wont have the full amount.

Errors

$ python $3$

vigenere.py $-e-d$

Error: Cannot have both encrypt and decrypt mode.

$ python$3$

vigenere.py $-$g $4$

Error: Program mode was not specified. Use $-$e for encrypt and $-$d for decrypt.

$ python$3$

vigenere.py

Error: Program mode was not specified. Use $-$e for encrypt and $-$ d for decrypt.

$ python$3$

vigenere.py $-g-$e

Error: You must supply an integer of at least zero with the grouping flag.

Handling user input

$ python $3$

vigenere.py $-$e

Enter the key: Habcd$1234$

Error: Keys must be at least $1$ character, and consist only of alphabetic characters.

Enter the key: Habcd

Enter the plaintext: HHello, World!

Ciphertext is: Hfnoo, Xqule!

$ python $3$

vigenere.py $-$e

Enter the key: $"$

Error: Keys must be at least $1$ character, and consist only of alphabetic characters.

Enter the key: Habcd

Enter the plaintext: #Hello, World!

Ciphertext is: Hfnoo, Xqule!

$ python $3$

vigenere.py $-$e

Enter the key: Habcd

Enter the plaintext: #

Ciphertext is:

It is okay for the user to not enter a message. The key is required, though. You should keep asking

for the key until a valid one is provided by the user.

Your program will be required to both encrypt and decrypt ciphertext. The mode is specified by a

program argument flag, $-$e for encrypt mode, and $-$d for decrypt mode.

Your program should work for both upper and lowercase plaintext$/$ciphertext$/$keys$,$ even if the key

and plaintext$/$ciphertext do not have the same case as eachother.

Your program should also have another option for grouping output characters together. This can be

specified by the $-g-g-e-d$