Reference no: EM131966135
Please help with the following programming problem(using python 3)
A Ceasar cipher is based on simply shifting the letters in the alphabet by a fixed amount. For example we might do the following:
Plain: ABCDEFGHIJKLMNOPQRSTUVWXYZ
Cipher: DEFGHIJKLMNOPQRSTUVWXYZABC
So each 'A' in the message is replaced by a 'D', each 'M' by a 'P', and so on. That is, there is a shift of 3 letters. Note that the alphabet wraps around at the end: An 'X' (third from the end) is replaced by an 'A', etc.
Design a function that takes two arguments, a string to encrypt and a shift value (an integer) to use for encrypting it, and returns the encrypted string. Apply the same shift to both lower and upper case letters. Do not alter the non-alphabetical characters (like space, comma etc).
Examples:
- Encrypting "Et tu, Brutus!" with a shift of 3 should return "Hw wx, Euxwxv!".
- (Wikipedia has a long list of Latin phrases if you want to encrypt more examples in Latin.)
- Encrypting "IBM" with a shift of -1 should return "HAL".
To decrypt a string, you can call the same function with the negative of the shift that was used to encrypt it. Also note that the function is invariant of the shift modulo 26: that is, a shift of 29 is the same as a shift of 3 (3 == 29 % 26), and a shift of -1 is the same as a shift of 25 (25 == -1 % 26).