#!/usr/bin/env python # coding: utf-8

# In[ ]:

# , import sys

def caesar_str_enc(plaintext, K): ciphertext="" for ch in plaintext: encch = caesar_ch_enc(ch, K) ciphertext = ciphertext + encch return ciphertext

def caesar_ch_enc(ch, K): # everything needed to map a char to its encoded char with K as the parameter return encch

def caesar_str_dec(ciphertext, K): plaintext = "" for ch in ciphertext: decch = caesar_ch_dec(ch, K) plaintext = plaintext + decch return plain text def caesar_ch_dec (ch, K): # ... return decch

def test_module(): #K = sys.argv[1] #input_str = sys.argv[2] K =3 input_str = "this is a test" print(input_str) encstr = caesar_str_enc(input_str, K) print(encstr) decstr = caesar_str_dec(encstr, K) print(decstr) #if __name__=="__main__": # test_module()

# In this case, if you call your file like this: # >python caear_hw.py 3 "string to be encoded" # it should first print the above string # then the encrypted version of it # and next the decrypted version of it i.e., the original one

complete the program so that it can be called from command line as:

>python caesar_hw.py 2 "a test sentence"

and the output should be 2 lines:

--first line will be the encrypted version of the given sentence with k=2:

c vguv ugpvgpeg

--second line should be the decrypted version of the first line with the same K value